Если ошибка то продолжить vba

Обработка ошибок в VBA Excel с помощью оператора On Error. Синтаксис выражений с оператором On Error. Пример кода с простым обработчиком ошибок.

On Error – это оператор, который используется для отслеживания ошибок во время исполнения кода VBA. При возникновении ошибки On Error передает информацию о ней в объект Err и включает программу обработки ошибок, начинающуюся с указанной строки.

В первую очередь, обработчик ошибок нужен для пользователей файлов Excel с кодами VBA. Любая ошибка приводит к прекращению выполнения программы, открытию редактора VBA с непонятным для пользователя сообщением или даже к полному зависанию приложения.

Обработчик ошибок позволяет завершить выполнение программы при возникновении ошибки и вывести сообщение пользователю с ее описанием.

Синтаксис выражений с On Error

Включает алгоритм обнаружения ошибок и, в случае возникновения ошибки, передает управление операторам обработчика ошибок с указанной в выражении строки. Stroka – это метка, после которой расположены операторы обработчика ошибок.

Включает алгоритм обнаружения ошибок и, в случае возникновения ошибки, передает управление оператору, следующему за оператором, вызвавшем ошибку.

Отключает любой включенный обработчик ошибок в текущей процедуре.

Простой обработчик ошибок

Шаблон простейшего обработчика ошибок:

Sub Primer() On Error GoTo Stroka     ‘Блок операторов процедуры Exit Sub Stroka:     MsgBox «Произошла ошибка: « & Err.Description End Sub

Оператор On Error GoTo размещается в начале процедуры, метка и обработчик ошибок – в конце процедуры. Название метки можно сменить на другое, в том числе на кириллице.

Оператор Exit Sub обеспечивает выход из процедуры, если блок операторов выполнен без ошибок. Для вывода описания ошибки используется свойство Description объекта Err.

Примеры обработки ошибок

Пример 1
Деление на ноль:

Sub Primer1() On Error GoTo Инструкция     Dim a As Double     a = 45 / 0 Exit Sub Instr:     MsgBox «Произошла ошибка: « & Err.Description End Sub

Результат выполнения кода VBA Excel с обработчиком ошибок:

Пример 2
Выход за границы диапазона:

Sub Primer2() On Error GoTo Instr     Dim myRange As Range     Set myRange = Range(«A1:D4»).Offset(—2) Exit Sub Instr:     MsgBox «Произошла ошибка: « & Err.Description End Sub

Результат выполнения кода VBA Excel с оператором On Error GoTo:

Пример использования выражений On Error Resume Next и On Error GoTo 0 смотрите в статье: Отбор уникальных значений с помощью Collection.

Error handling refers to the way runtime errors are handled. Error handling in VBA is done using the On Error statement and the Err object. Runtime errors can be generated by attempting to execute error-causing code or they can be raised explicitly using the Err.Raise method. There are a number of built-in types of runtime errors, and custom errors can be defined as well. Each type of runtime error has a unique number which can be used to determine at runtime which type of error has occurred and respond accordingly.

On Error

The On Error statement is used to control what happens when a runtime error occurs. The On Error statement sets or removes the current error handling scope. When a runtime error occurs in VBA the error trap is triggered and if an On Error statement has been set, VBA will respond according to which type of On Error statement was used.

Statement	Description
On Error Resume Next	Skips lines of code that cause errors. Use with caution.
On Error GoTo Line	When an error occurs execution will jump to a specified label or line number.
On Error GoTo 0	Clears the current error and disables error handling.
On Error GoTo -1	Clears the current error and resets the error trap.
Resume	When used after the On Error GoTo statement, Resume will continue execution from the line of code that caused the error.
Resume Next	When used after the On Error GoTo statement, Resume Next will continue execution from the line of code directly after the line that caused the error.
Resume Line	When used after the On Error GoTo statement, Resume Line will jump to a specified label or line number and continue execution.

On Error Resume Next

Public Sub Example()

    On Error Resume Next

    Err.Raise 1004

    Debug.Print "Error was skipped"

End Sub

On Error GoTo Line

Public Sub Example()

    On Error GoTo HandleError

    Err.Raise 1004

    Exit Sub

HandleError:
    Debug.Print "Error Handled"

End Sub

Note: It is not recommended to use line numbers.

Public Sub Example() 
10
20  On Error GoTo 80
30
40  Err.Raise 1004
50
60  Exit Sub
70
80  Debug.Print "Error Handled"
90
End Sub

On Error GoTo…Resume

Public Sub Example()

    Dim N As Long
    N = 0

    On Error GoTo HandleError

    'Divide by zero error will be fixed by error handler
    Debug.Print 1 / N

    Debug.Print "Error Handled."

    Exit Sub

HandleError:
    If Err.Number = 11 Then
        Debug.Print "Handling 'Division by zero' Error..."
        N = 1
        Resume
    Else
        Err.Raise Err.Number
    End If

End Sub

On Error GoTo…Resume Next

Public Sub Example()

    On Error GoTo HandleError

    Err.Raise 1004

    Debug.Print "Error Handled. Resuming Next..."

    Exit Sub

HandleError:
    Debug.Print "Handling Error..."
    Resume Next

End Sub

On Error GoTo…Resume Line

Public Sub Example()

    On Error GoTo HandleError

    Err.Raise 1004

Continue:
    Debug.Print "Resuming..."

    Exit Sub

HandleError:
    Debug.Print "Error Handled"
    Resume Continue

End Sub

Note: It is not recommended to use line numbers.

Public Sub Example()
10
20    On Error GoTo 100
30
40    Err.Raise 1004
50
60    Debug.Print "Resuming..."
70
80    Exit Sub
90
100   Debug.Print "Error Handled"
110   Resume 60
120
End Sub

On Error GoTo 0

Public Sub Example()

    On Error Resume Next

    Err.Raise 1004 'Error will be skipped

    On Error GoTo 0

    Err.Raise 1004 'Error will be raised

End Sub

On Error GoTo -1

Public Sub Example()

    On Error GoTo HandleError1

    Err.Raise 1004

    Exit Sub

HandleError1:
    Debug.Print "HandleError1"
    On Error GoTo -1
    On Error GoTo HandleError2
    Err.Raise 1004
    Exit Sub

HandleError2:
    Debug.Print "HandleError2"
    Exit Sub

End Sub

The Err Object

The Err Object is used to access information about a runtime error that has occurred. When a runtime error occurs, the Err object’s properties are filled with information about the error. The Err object can also be used to raise errors explicitly.

Member	Description
Clear	Clears properties of the Err object. Does NOT reset error trap or clear error handling scope.
Description	A text description of the error.
HelpContext	The context ID for a topic in a help file.
HelpFile	The path to help file.
LastDllError	Returns a system error code produced by a call to a dynamic-link library (DLL). Read-only. Always returns zero on Mac.
Number	The error number, 0 through 65535.
Raise	Raises a specified runtime error.
Source	The name of the object or application that originated the error.

The Err Object is a Singleton

The Err object has a single default global instance and cannot be instantiated. The Err object can be accessed anywhere in VBA just by typing Err.

Public Sub Example()

    Err.Raise 1004 'No need to instantiate Err object

End Sub

Public Sub Example()

    Dim E As ErrObject
    Set E = New ErrObject 'Causes error

End Sub

Properties

The Err object’s properties are filled with data when a runtime error occurs. The Number property is especially important because it can be used to dynamically respond to different types of errors. If no runtime error has occurred, the Number property will be 0. Therefore, to determine if an error has occurred in a particular line, the Number property can be checked to see if it is 0 or not.

Public Sub Example()

    On Error Resume Next

    Err.Raise 1004

    If Err.Number <> 0 Then

        With Err
            Debug.Print "Number: " & .Number
            Debug.Print "Description: " & .Description
            Debug.Print "Source: " & .Source
            Debug.Print "HelpFile: " & .HelpFile
            Debug.Print "HelpContext: " & .HelpContext
            Debug.Print "LastDllError: " & .LastDllError
        End With

        Err.Raise Err.Number

    Else

        Debug.Print "No Error"

    End If

End Sub

Clearing The Err Object

The Err object can be reset in a few different ways. The Err object is reset when Err.Clear is called, a Resume or Resume Next statement is executed for the error, or another On Error statement is executed. Exiting an error-causing procedure does not reset the Err object.

Note: Exiting an error-causing procedure does not reset the Err object.

Public Sub Example()

    Call ErrorCausingProcedure1
    Debug.Print Err.Number 'Prints 1004

    Call ErrorCausingProcedure2
    Debug.Print Err.Number 'Prints 0

    Call ErrorCausingProcedure3
    Debug.Print Err.Number 'Prints 0

    Call ErrorCausingProcedure4
    Debug.Print Err.Number 'Prints 0

End Sub

Public Sub ErrorCausingProcedure1()
    'Exiting procedure doe NOT reset the Err object
    On Error Resume Next
    Err.Raise 1004
End Sub

Public Sub ErrorCausingProcedure2()
    'Calling Err.Clear resets the Err object
    On Error Resume Next
    Err.Raise 1004
    Err.Clear
End Sub

Public Sub ErrorCausingProcedure3()
    'Resume Next resets the Err object
    On Error GoTo HandleError
    Err.Raise 1004
    Exit Sub
HandleError:
    Resume Next
End Sub

Public Sub ErrorCausingProcedure4()
    'On Error statement resets the Err object
    On Error Resume Next
    Err.Raise 1004
    On Error GoTo 0
End Sub

Calling Err.Clear only clears the Err object. Err.Clear does not reset the error handling trap or end the error handling scope. On Error GoTo -1 will clear the Err object and reset error trapping, allowing another error to be raised. On Error GoTo 0 will clear the Err object and clear the error handling scope.

Public Sub Example()

    On Error Resume Next

    'Error is skipped
    Err.Raise 1004

    'Prints 1004
    Debug.Print Err.Number

    'Err object is reset
    Err.Clear

    'Prints 0
    Debug.Print Err.Number

    'Error is skipped because error handling scope was not reset
    Err.Raise 1004

    'Prints 1004
    Debug.Print Err.Number

    'Clears Err object and error handling scope
    On Error GoTo 0

    'Prints 0
    Debug.Print Err.Number

    'Raises a runtime error
    Err.Raise 1004

End Sub

Error Trapping Options

Error Trapping options can be selected which can override error handling code in VBA. To change error trapping options navigate to Tools → Options → General in the Visual Basic Editor.

Option	Description
Break on All Errors	Will enter break mode when any error is encountered regardless of error handling code.
Break in Class Module	Will enter break mode and show errors inside class modules.
Break on Unhandled Errors	This is the default setting. Will enter break mode when an error is encountered and it is not handled by code.

CVErr Function

The CVErr function can be used to return an error from a function. CVErr returns a value of type Variant with subtype Error. Only variables of type Variant can be assigned a value using the CVErr function. CVErr can take any error number as an argument. CVErr can be used to return a cell error from a user-defined function that is intended for use in spreadsheets.

Option Explicit

Public Function ReturnValueError() As Variant

    'Shows #VALUE Error in cell
    ReturnValueError = CVErr(xlErrValue)

End Function

xlErr Cell Errors

xlErr Constant	Cell Error
xlErrBlocked	#BLOCKED!
xlErrCalc	#CALC!
xlErrConnect	#CONNECT!
xlErrDiv0	#DIV/0!
xlErrField	#FIELD!
xlErrGettingData	#GETTING_DATA
xlErrNA	#N/A
xlErrName	#NAME?
xlErrNull	#NULL!
xlErrNum	#NUM!
xlErrRef	#REF!
xlErrSpill	#SPILL!
xlErrUnknown	#UNKNOWN!
xlErrValue	#VALUE!

IsError Function

The IsError function returns True if the argument expression evaluates to an error. IsError can be used to test if a cell value contains an error or a user-defined function returns an error. To return an error from a function use the CVErr function.

Option Explicit

Public Sub Example()

    If IsError(Range("A1").Value) Then
        Debug.Print "Range A1 contains an error."
    End If

    Dim E As Variant
    E = ReturnError()

    If IsError(E) Then
        Debug.Print "E is Error: " & CStr(E)
    End If

End Sub

Public Function ReturnError() As Variant

    ReturnError = CVErr(xlErrValue)

End Function

Error Function

The Error/Error$ function is used to return the description text of an error. The Error function can be used to return a specific error description based on an error number or it can return the description text of the last error to occur.

Specific Error Description

Pass the optional ErrorNumber argument to the Error function to return a specific error description. Although the Error function can take a number between -2147483648 and 65535, it should be intended for use with the range 0 through 65535. If the error number is outside the valid range an Overflow runtime error will occur. If the error number is within the valid range but is not defined, the message «Application-defined or object-defined error» will be returned.

Public Sub Example()

    Debug.Print Error(5) 'Prints: Invalid procedure call or argument

End Sub

Most Recent Error Description

Call the Error function with no ErrorNumber argument to return the description text for the last error to occur. If no error has occurred, a zero-length string will be returned. The Err.Description property can be used to get the text description of the most recent runtime error instead of using the Error function.

Public Sub Example()

    On Error Resume Next

    Err.Raise 5

    Debug.Print Error() 'Prints: Invalid procedure call or argument

End Sub

Raising Errors

Use the Err.Raise method to raise a runtime error. Errors should be raised when an unacceptable state has been reached in a program. Existing VBA error numbers can be used to raise errors or custom error numbers can be created.

Raising Existing Errors

An appropriate VBA error number can be selected which describes the error.

Public Function RandomLong(MinValue As Long, MaxValue As Long) As Long

    If MinValue > MaxValue Then
        Err.Raise 5
    End If

    Randomize
    RandomLong = Int((MaxValue - MinValue + 1) * Rnd + MinValue)

End Function

User-Defined Errors

To raise a user-defined error, create an error number by using the vbObjectError constant and adding a number between 513 and 65535. The range 0 through 512 is reserved for system errors. The vbObjectError constant has the value -2147221504 so user-defined errors will be negative. To derive the positive portion of a user-defined error simply subtract the vbObjectError constant from the error number.

Public Sub Example()

    On Error GoTo HandleError

    Err.Raise Number:=vbObjectError + 513, Description:="Custom Error"

    Exit Sub

HandleError:
    Debug.Print Err.Number - vbObjectError, Err.Description 'Prints: 513 Custom Error
    Resume Next

End Sub

Error Statement

The Error statement raises a runtime error for a given error number. The Error statement is included for backward compatibility with older versions of VBA and Err.Raise should be used instead for new code.

Public Sub Example()

    'Backward compatible
    Error 5

    'Use this for new code
    Err.Raise 5

End Sub

Error Numbers

Runtime errors each have a number used to identify what type of error it is. Error numbers can be used with the Err.Raise method, the Error statement, and the Error function. When a runtime error occurs, the Err.Number property will be set to the number associated with the type of error. Any positive error number not listed in the table below returns «Application-defined or object-defined error».

Error Number	Error Text
3	Return without GoSub
5	Invalid procedure call or argument
6	Overflow
7	Out of memory
9	Subscript out of range
10	This array is fixed or temporarily locked
11	Division by zero
13	Type mismatch
14	Out of string space
16	Expression too complex
17	Can’t perform requested operation
18	User interrupt occurred
20	Resume without error
28	Out of stack space
35	Sub or Function not defined
47	Too many DLL application clients
48	Error in loading DLL
49	Bad DLL calling convention
51	Internal error
52	Bad file name or number
53	File not found
54	Bad file mode
55	File already open
57	Device I/O error
58	File already exists
59	Bad record length
61	Disk full
62	Input past end of file
63	Bad record number
67	Too many files
68	Device unavailable
70	Permission denied
71	Disk not ready
74	Can’t rename with different drive
75	Path/File access error
76	Path not found
91	Object variable or With block variable not set
92	For loop not initialized
93	Invalid pattern string
94	Invalid use of Null
96	Unable to sink events of object because the object is already firing events to the maximum number of event receivers that it supports
97	Can not call friend function on object which is not an instance of defining class
98	A property or method call cannot include a reference to a private object, either as an argument or as a return value
321 (1 — 2)	Invalid file format
322	Can’t create necessary temporary file
325	Invalid format in resource file
380 (1 — 2)	Invalid property value
381	Invalid property array index
382	Set not supported at runtime
383	Set not supported (read-only property)
385	Need property array index
387	Set not permitted
393	Get not supported at runtime
394	Get not supported (write-only property)
422	Property not found
423	Property or method not found
424	Object required
429	ActiveX component can’t create object
430	Class does not support Automation or does not support expected interface
432	File name or class name not found during Automation operation
438	Object doesn’t support this property or method
440	Automation error
442	Connection to type library or object library for remote process has been lost. Press OK for dialog to remove reference.
443	Automation object does not have a default value
445	Object doesn’t support this action
446	Object doesn’t support named arguments
447	Object doesn’t support current locale setting
448	Named argument not found
449	Argument not optional
450	Wrong number of arguments or invalid property assignment
451	Property let procedure not defined and property get procedure did not return an object
452	Invalid ordinal
453	Specified DLL function not found
454	Code resource not found
455	Code resource lock error
457	This key is already associated with an element of this collection
458	Variable uses an Automation type not supported in Visual Basic
459	Object or class does not support the set of events
460 (1 — 2)	Invalid clipboard format
461	Method or data member not found
462	The remote server machine does not exist or is unavailable
463	Class not registered on local machine
481 (1 — 2)	Invalid picture
482 (1 — 2)	Printer error
735	Can’t save file to TEMP
744	Search text not found
746	Replacements too long
1004	Application-defined or object-defined error
31001	Application-defined or object-defined error. *Out of memory
31004	Application-defined or object-defined error. *No object
31018	Application-defined or object-defined error. *Class is not set
31027	Application-defined or object-defined error. *Unable to activate object
31032	Application-defined or object-defined error. *Unable to create embedded object
31036	Application-defined or object-defined error. *Error saving to file
31037	Application-defined or object-defined error. *Error loading from file

“Abort, Retry, Fail?” – MS-DOS error message circa 1986

This post provides a complete guide to VBA Error Handing. If you are looking for a quick summary then check out the quick guide table in the first section.

If you are looking for a particular topic on VBA Error Handing then check out the table of contents below(if it’s not visible click on the post header).

If you are new to VBA Error Handling, then you can read the post from start to finish as it is laid out in logical order.

A Quick Guide to Error Handing

Item	Description
On Error Goto 0	When error occurs, the code stops and displays the error.
On Error Goto -1	Clears the current error setting and reverts to the default.
On Error Resume Next	Ignores the error and continues on.
On Error Goto [Label]	Goes to a specific label when an error occurs. This allows us to handle the error.
Err Object	When an error occurs the error information is stored here.
Err.Number	The number of the error. (Only useful if you need to check a specific error occurred.)
Err.Description	Contains the error text.
Err.Source	You can populate this when you use Err.Raise.
Err.Raise	A function that allows you to generate your own error.
Error Function	Returns the error text from an error number. Obsolete.
Error Statement	Simulates an error. Use Err.Raise instead.

The Webinar

Members of the Webinar Archives can access the webinar for this article by clicking on the image below.

(Note: Archive members have access to the webinar archive.)

Download the Error Handling Library

Introduction

Error Handling refers to code that is written to handle errors which occur when your application is running. These errors are normally caused by something outside your control like a missing file, database being unavailable, data being invalid etc.

If we think an error is likely to occur at some point, it is good practice to write specific code to handle the error if it occurs and deal with it.

For all other errors, we use generic code to deal with them. This is where the VBA error handling statement comes into play. They allow our application to deal gracefully with any errors we weren’t expecting.

To understand error handling we must first understand the different types of errors in VBA.

VBA Errors

There are three types of errors in VBA:

1. Syntax
2. Compilation
3. Runtime

We use error handling to deal with runtime errors. Let’s have a look at each of these error types so that it is clear what a runtime error is.

Syntax Errors

If you have used VBA for any length of time you will have seen a syntax error. When you type a line and press return, VBA will evaluate the syntax and if it is not correct it will display an error message.

For example if you type If and forget the Then keyword, VBA will display the following error message

Some examples of syntax errors are

' then is missing
If a > b

' equals is missing after i
For i 2 To 7

' missing right parenthesis
b = left("ABCD",1

Syntax errors relate to one line only. They occur when the syntax of one line is incorrect.

Note: You can turn off the Syntax error dialog by going to Tools->Options and checking off “Auto Syntax Check”. The line will still appear red if there is an error but the dialog will not appear.

Compilation Errors

Compilation errors occur over more than one line. The syntax is correct on a single line but is incorrect when all the project code is taken into account.

Examples of compilation errors are:

• If statement without corresponding End If statement
• For without Next
• Select without End Select
• Calling a Sub or Function that does not exist
• Calling a Sub or Function with the wrong parameters
• Giving a Sub or Function the same name as a module
• Variables not declared(Option Explicit must be present at the top of the module)

The following screenshot shows a compilation error that occurs when a For loop has no matching Next statement.

Using Debug->Compile

To find compilation errors, we use Debug->Compile VBA Project from the Visual Basic menu.

When you select Debug->Compile, VBA displays the first error it comes across.

When this error is fixed, you can run Compile again and VBA will then find the next error.

Debug->Compile will also include syntax errors in it’s search which is very useful.

If there are no errors left and you run Debug->Compile , it may appear that nothing happened. However, “Compile” will be grayed out in the Debug menu. This means your application has no compilation errors at the current time.

Debug->Compile Error Summary

• Debug->Compile finds compilation(project wide) errors.
• It will also find syntax errors.
• It finds one error each time you use it.
• When there are no compilation errors left the Compile option will appear grayed out in the menu.

Debug->Compile Usage

You should always use Debug->Compile before you run your code. This ensures that your code has no compilation errors when you run it.

If you do not run Debug->Compile then VBA may find compile errors when it runs. These should not be confused with Runtime errors.

Runtime Errors

Runtime errors occur when your application is running. They are normally outside of your control but can be caused by errors in your code.

For example, imagine your application reads from an external workbook. If this file gets deleted then VBA will display an error when your code tries to open it.

Other examples of runtime errors are

• a database not being available
• the user entering invalid data
• a cell containing text instead of a number

As we have seen, the purpose of error handling is to deal with runtime errors when they occur.

Expected Versus Unexpected Errors

When we think a runtime error could occur we put code in place to handle it. For example, we would normally put code in place to deal with a file not being found.

The following code checks if the file exists before it tries to open it. If the file does not exist then a user friendly message is displayed and the code exits the sub.

' https://excelmacromastery.com/
Sub OpenFile()
    
    Dim sFile As String
    sFile = "C:\docs\data.xlsx"
    
    ' Use Dir to check if file exists
    If Dir(sFile) = "" Then
        ' if file does not exist display message
        MsgBox "Could not find the file " & sFile
        Exit Sub
    End If
    
    ' Code will only reach here if file exists
    Workbooks.Open sFile
    
End Sub

When we think an error is likely to occur at some point, it is good practice to add code to handle the situation. We normally refer to these errors as expected errors.

If we don’t have specific code to handle an error it is considered an unexpected error. We use the VBA error handling statements to handle the unexpected errors.

Runtime Errors that are not VBA Errors

Before we look at the VBA Handling there is one type of error we must mention. Some runtime errors are not considered errors by VBA but only by the user.

Let me explain this with an example. Imagine you have an application that requires you to add the values in the variables a and b

result = a + b

Let’s say you mistakenly use an asterisk instead of the plus sign

result = a * b

This is not a VBA error. Your code syntax is perfectly legal. However, from your requirements point of view it is an error.

These errors cannot be dealt with using error handling as they obviously won’t generate any error. You can deal with these errors using Unit Testing and Assertions. I have an in-depth post about using VBA assertions – see How to Make Your Code BulletProof.

The On Error Statement

As we have seen there are two ways to treat runtime errors

1. Expected errors – write specific code to handle them.
2. Unexpected errors – use VBA error handling statements to handle them.

The VBA On Error statement is used for error handling. This statement performs some action when an error occurs during runtime.

There are four different ways to use this statement

1. On Error GoTo 0 – the code stops at the line with the error and displays a message.
2. On Error Resume Next – the code moves to next line. No error message is displayed.
3. On Error GoTo [label] – the code moves to a specific line or label. No error message is displayed. This is the one we use for error handling.
4. On Error GoTo -1 – clears the current error.

Let’s look at each of these statements in turn.

On Error GoTo 0

This is the default behavior of VBA. In other words, if you don’t use On Error then this is the behavior you will see.

When an error occurs, VBA stops on the line with the error and displays the error message. The application requires user intervention with the code before it can continue. This could be fixing the error or restarting the application. In this scenario no error handling takes place.

Let’s look at an example. In the following code, we have not used any On Error line so VBA will use the On Error GoTo 0 behavior by default.

' https://excelmacromastery.com/
Sub UsingDefault()

    Dim x As Long, y As Long
    
    x = 6
    y = 6 / 0
    x = 7

End Sub

The second assignment line results in a divide by zero error. When we run this code we will get the error message shown in the screenshot below

When the error appears you can choose End or Debug

If you select End then the application simply stops.
If you select Debug the application stops on the error line as the screenshot below shows

This behaviour is fine when you are writing VBA code as it shows you the exact line with the error.

This behavior is unsuitable for an application that you are given to a user. These errors look unprofessional and they make the application look unstable.

An error like this is essentially the application crashing. The user cannot continue on without restarting the application. They may not use it at all until you fix the error for them.

By using On Error GoTo [label] we can give the user a more controlled error message. It also prevents the application stopping. We can get the application to perform in a predefined manner.

On Error Resume Next

Using On Error Resume Next tells VBA to ignore the error and continue on.

There are specific occasions when this is useful. Most of the time you should avoid using it.

If we add Resume Next to our example Sub then VBA will ignore the divide by zero error

' https://excelmacromastery.com/
Sub UsingResumeNext()

    On Error Resume Next
    
    Dim x As Long, y As Long
    
    x = 6
    y = 6 / 0
    x = 7

End Sub

It is not a good idea to do this. If you ignore the error, then the behavior can be unpredictable. The error can affect the application in multiple ways.You could end up with invalid data. The problem is that you aren’t aware that something went wrong because you have suppressed the error.

The code below is an example of where using Resume Next is valid

' https://excelmacromastery.com/
Sub SendMail()

   On Error Resume Next
   
    ' Requires Reference:
    ' Microsoft Outlook 15.0 Object Library
    Dim Outlook As Outlook.Application
    Set Outlook = New Outlook.Application

    If Outlook Is Nothing Then
        MsgBox "Cannot create Microsoft Outlook session." _
                   & " The email will not be sent."
        Exit Sub
    End If
    
End Sub

In this code we are checking to see if Microsoft Outlook is available on a computer. All we want to know is if it is available or not. We are not interested in the specific error.

In the code above, we continue on if there is an error. Then in the next line we check the value of the Outlook variable. If there has been an error then the value of this variable will be set to Nothing.

This is an example of when Resume could be useful. The point is that even though we use Resume we are still checking for the error. The vast majority of the time you will not need to use Resume.

On Error GoTo [label]

This is how we use Error Handling in VBA. It is the equivalent of the Try and Catch functionality you see in languages such as C# and Java.

When an error occurs you send the error to a specific label. It is normally at the bottom of the sub.

Let’s apply this to the sub we have been using

' https://excelmacromastery.com/
Sub UsingGotoLine()

    On Error GoTo eh
    
    Dim x As Long, y As Long
    
    x = 6
    y = 6 / 0
    x = 7
    
Done:
    Exit Sub
eh:
    MsgBox "The following error occurred: " & Err.Description
End Sub

The screenshot below shows what happens when an error occurs

VBA jumps to the eh label because we specified this in the On Error Goto line.

Note 1: The label we use in the On…GoTo statement, must be in the current Sub/Function. If not you will get a compilation error.

Note 2: When an error occurs when using On Error GoTo [label], the error handling returns to the default behaviour i.e. The code will stop on the line with the error and display the error message. See the next section for more information about this.

On Error GoTo -1

This statement is different than the other three. It is used to clear the current error rather than setting a particular behaviour.

When an error occurs using On Error GoTo [label], the error handling behaviour returns to the default behaviour i.e. “On Error GoTo 0”. That means that if another error occurs the code will stop on the current line.

This behaviour only applies to the current sub. Once we exit the sub, the error will be cleared automatically.

Take a look at the code below. The first error will cause the code to jump to the eh label. The second error will stop on the line with the 1034 error.

' https://excelmacromastery.com/
Sub TwoErrors()

    On Error Goto eh
        
    ' generate "Type mismatch" error
    Error (13)

Done:
    Exit Sub
eh:
    ' generate "Application-defined" error
    Error (1034)
End Sub

If we add further error handling it will not work as the error trap has not been cleared.

In the code below we have added the line

On Error Goto eh_other

after we catch the first error.

This has no effect as the error has not been cleared. In other words the code will stop on the line with the error and display the message.

' https://excelmacromastery.com/
Sub TwoErrors()

    On Error Goto eh
        
    ' generate "Type mismatch" error
    Error (13)

Done:
    Exit Sub
eh:
    On Error Goto eh_other
    ' generate "Application-defined" error
    Error (1034)
Exit Sub
eh_other:
    Debug.Print "eh_other " & Err.Description
End Sub

To clear the error we use On Error GoTo -1. Think of it like setting a mouse trap. When the trap goes off you need to set it again.

In the code below we add this line and the second error will now cause the code to jump to the eh_other label

' https://excelmacromastery.com/
Sub TwoErrors()

    On Error Goto eh
        
    ' generate "Type mismatch" error
    Error (13)

Done:
    Exit Sub
eh:
    ' clear error
    On Error Goto -1
    
    On Error Goto eh_other
    ' generate "Application-defined" error
    Error (1034)
Exit Sub
eh_other:
    Debug.Print "eh_other " & Err.Description
End Sub

Note 1: There are probably rare cases where using On Error GoTo -1 is useful. In most cases using Resume Next is better as it clears the error and resumes the code at the next line after the error occurs.

Note 2: The Err Object has a member Clear. Using Clear clears the text and numbers in the Err object, but it does NOT reset the error.

Using On Error

As we have seen, VBA will do one of three things when an error occurs

• Stop and display the error.
• Ignore the error and continue on.
• Jump to a specific line.

VBA will always be set to one of these behaviors. When you use On Error, VBA will change to the behaviour you specify and forget about any previous behavior.

In the following Sub, VBA changes the error behaviour each time we use the On Error statement

' https://excelmacromastery.com/
Sub ErrorStates()

    Dim x As Long
    
    ' Go to eh label if error
    On Error Goto eh
    
    ' this will ignore the error on the following line
    On Error Resume Next
    x = 1 / 0
    
    ' this will display an error message on the following line
    On Error Goto 0
    x = 1 / 0
  
Done:  
   Exit Sub
eh:
    Debug.Print Err.Description
End Sub

Resume Next

The Resume Next statement is used to clear the error and then resume the code from the line after where the error occurred.

If your code can have multiple errors and you want to keep detecting them then this line is very useful.

For example, in the following code we want to resume the code after the error has been reported:

Private Sub Main()

    On Error Goto eh
    
    Dim i As Long
    For i = 1 To 3
        ' Generate type mismatch error
         Error 13
    Next i

done:
    Exit Sub
eh:
    Debug.Print i, Err.Description
End Sub

 
We could use On Error Goto -1 to clear the code and then use a goto statement to go back to the code like this:

Private Sub Main()

    On Error Goto eh
    
    Dim i As Long
    For i = 1 To 3
        ' Generate type mismatch error
         Error 13
continue:
    Next i

done:
    Exit Sub
eh:
    Debug.Print i, Err.Description
    On Error Goto -1 ' clear the error
    Goto continue ' return to the code
End Sub

 
The Resume Next provides a nicer way of doing it and it always means the code is much clearer and easier to understand:

Private Sub Main()

    On Error Goto eh
    
    Dim i As Long
    For i = 1 To 3
        ' Generate type mismatch error
         Error 13
continue:
    Next i

done:
    Exit Sub
eh:
    Debug.Print i, Err.Description
    ' clear the error and return to the code
    Resume Next  
End Sub

The Err Object

When an error occurs you can view details of the error using the Err object.

When an runtime error occurs, VBA automatically fills the Err object with details.

The code below will print “Error Number: 13 Type Mismatch” which occurs when we try to place a string value in the long integer total

' https://excelmacromastery.com/
Sub UsingErr()

    On Error Goto eh
    
    Dim total As Long
    total = "aa"

Done:
    Exit Sub
eh:
    Debug.Print "Error number: " & Err.Number _
            & " " & Err.Description
End Sub

The Err.Description provides details of the error that occurs. This is the text you normally see when an error occurs e.g. “Type Mismatch”

The Err.Number is the ID number of the error e.g. the error number for “Type Mismatch” is 13. The only time you really need this is if you are checking that a specific error occurred and this is only necessary on rare occasions.

The Err.Source property seems like a great idea but it does not work for a VBA error. The source will return the project name, which hardly narrows down where the error occurred. However, if you create an error using Err.Raise you can set the source yourself and this can be very useful.

Getting the Line Number

The Erl function is used to return the line number where the error occurs.

It often causes confusion. In the following code, Erl will return zero

' https://excelmacromastery.com/
Sub UsingErr()

    On Error Goto eh
    
    Dim val As Long
    val = "aa"

Done:
    Exit Sub
eh:
    Debug.Print Erl
End Sub

This is because there are no line numbers present. Most people don’t realise it but VBA allows you to have line numbers.

If we change the Sub above to have line number it will now print out 20

' https://excelmacromastery.com/
Sub UsingErr()

10        On Error Goto eh
          
          Dim val As Long
20        val = "aa"

Done:
30        Exit Sub
eh:
40        Debug.Print Erl
End Sub

Adding line numbers to your code manually is cumbersome. However there are tools available that will allow you to easily add and remove line numbers to a sub.

When you are finished working on a project and hand it over to the user it can be useful to add line numbers at this point. If you use the error handling strategy in the last section of this post, then VBA will report the line where the error occurred.

Using Err.Raise

Err.Raise allows us to create errors. We can use it to create custom errors for our application which is very useful. It is the equivalent of the Throw statement in Java\C#.

The format is as follows

Err.Raise [error number], [error source], [error description]

Let’s look at a simple example. Imagine we want to ensure that a cell has an entry that has a length of 5 characters. We could have a specific message for this

' https://excelmacromastery.com/
Public Const ERROR_INVALID_DATA As Long = vbObjectError + 513

Sub ReadWorksheet()

    On Error Goto eh
    
    If Len(Sheet1.Range("A1")) <> 5 Then
        Err.Raise ERROR_INVALID_DATA, "ReadWorksheet" _
            , "The value in the cell A1 must have exactly 5 characters."
    End If
    
    ' continue on if cell has valid data
    Dim id As String
    id = Sheet1.Range("A1")
    

Done:
    Exit Sub
eh:
    ' Err.Raise will send code to here
    MsgBox "Error found: " & Err.Description
End Sub

When we create an error using Err.Raise we need to give it a number. We can use any number from 513 to 65535 for our error. We must use vbObjectError with the number e.g.

Err.Raise vbObjectError + 513

Using Err.Clear

Err.Clear is used to clear the text and numbers from the Err.Object. In other words, it clears the description and number.If you want the clear the actual error you can use either On Error GoTo -1 or Resume Next

It is rare that you will need to use Err.Clear but let’s have a look at an example where you might.

In the code below we are counting the number of errors that will occur. To keep it simple we are generating an error for each odd number.

We check the error number each time we go through the loop. If the number does not equal zero then an error has occurred. Once we count the error we need to set the error number back to zero so it is ready to check for the next error.

' https://excelmacromastery.com/
Sub UsingErrClear()

    Dim count As Long, i As Long

    ' Continue if error as we will check the error number
    On Error Resume Next
    
    For i = 0 To 9
        ' generate error for every second one
        If i Mod 2 = 0 Then Error (13)
        
        ' Check for error
        If Err.Number <> 0 Then
            count = count + 1
            Err.Clear    ' Clear Err once it is counted
        End If
    Next

    Debug.Print "The number of errors was: " & count
End Sub

Note 1: Err.Clear resets the text and numbers in the error object but it does not clear the error – see Resume Next Or On Error GoTo -1 for more information about clearing the actual error.

Logging

Logging means writing information from your application when it is running. When an error occurs you can write the details to a text file so you have a record of the error.

The code below shows a very simple logging procedure

' https://excelmacromastery.com/
Sub Logger(sType As String, sSource As String, sDetails As String)
    
    Dim sFilename As String
    sFilename = "C:\temp\logging.txt"
    
    ' Archive file at certain size
    If FileLen(sFilename) > 20000 Then
        FileCopy sFilename _
            , Replace(sFilename, ".txt", Format(Now, "ddmmyyyy hhmmss.txt"))
        Kill sFilename
    End If
    
    ' Open the file to write
    Dim filenumber As Variant
    filenumber = FreeFile 
    Open sFilename For Append As #filenumber
    
    Print #filenumber, CStr(Now) & "," & sType & "," & sSource _
                                & "," & sDetails & "," & Application.UserName
    
    Close #filenumber
    
End Sub

You can use it like this

' Create unique error number
' https://excelmacromastery.com/
Public Const ERROR_DATA_MISSING As Long = vbObjectError + 514

Sub CreateReport()

    On Error Goto eh
    
    If Sheet1.Range("A1") = "" Then
       Err.Raise ERROR_DATA_MISSING, "CreateReport", "Data is missing from Cell A1"
    End If

    ' other code here
Done:
    Exit Sub
eh:
    Logger "Error", Err.Source, Err.Description
End Sub

The log is not only for recording errors. You can record other information as the application runs. When an error occurs you can then check the sequence of events before an error occurred.

Below is an example of logging. How you implement logging really depends on the nature of the application and how useful it will be:

' https://excelmacromastery.com/
Sub ReadingData()
    
    Logger "Information", "ReadingData()", "Starting to read data."
       
    Dim coll As New Collection
    ' add data to the collection
    coll.Add "Apple"
    coll.Add "Pear"
    
    If coll.Count < 3 Then
        Logger "Warning", "ReadingData()", "Number of data items is low."
    End If
    Logger "Information", "ReadingData()", "Number of data items is " & coll.Count
    
    Logger "Information", "ReadingData()", "Finished reading data."

End Sub

Having a lot of information when dealing with an error can be very useful. Often the user may not give you accurate information about the error that occurred. By looking at the log you can get more accurate information about the information.

This section covers some of the other Error Handling tools that VBA has. These items are considered obsolete but I have included them as they may exist in legacy code.

Error Function

The Error Function is used to print the error description from a given error number. It is included in VBA for backward compatibility and is not needed because you can use the Err.Description instead.

Below are some examples:

' Print the text "Division by zero"
Debug.Print Error(11)
' Print the text "Type mismatch"
Debug.Print Error(13)
' Print the text "File not found"
Debug.Print Error(53)

Error Statement

The Error statement allows you to simulate an error. It is included in VBA for backward compatibility. You should use Err.Raise instead.

In the following code we simulate a “Divide by zero” error.

' https://excelmacromastery.com/
Sub SimDivError()

    On Error Goto eh
        
    ' This will create a division by zero error
    Error 11
    
    Exit Sub
eh:
    Debug.Print Err.Number, Err.Description
End Sub

This statement is included in VBA for backward compatibility. You should use Err.Raise instead.

A Simple Error Handling Strategy

With all the different options you may be confused about how to use error handling in VBA. In this section, I’m going to show you how to implement a simple error handling strategy that you can use in all your applications.

The Basic Implementation

This is a simple overview of our strategy

1. Place the On Error GoTo Label line at the start of our topmost sub.
2. Place the error handling Label at the end of our topmost sub.
3. If an expected error occurs then handle it and continue.
4. If the application cannot continue then use Err.Raise to jump to the error handling label.
5. If an unexpected error occurs the code will automatically jump to the error handling label.

The following image shows an overview of how this looks

The following code shows a simple implementation of this strategy:

' https://excelmacromastery.com/
Public Const ERROR_NO_ACCOUNTS As Long = vbObjectError + 514

Sub BuildReport()

    On Error Goto eh
    
    ' If error in ReadAccounts then jump to error
    ReadAccounts
    
    ' Do something with the code
    
Done:
    Exit Sub
eh:
    ' All errors will jump to here
    MsgBox Err.Source & ": The following error occured  " & Err.Description
End Sub

Sub ReadAccounts()
    
    ' EXPECTED ERROR - Can be handled by the code
    ' Application can handle A1 being zero
    If Sheet1.Range("A1") = 0 Then
        Sheet1.Range("A1") = 1
    End If
    
    ' EXPECTED  ERROR - cannot be handled by the code
    ' Application cannot continue if no accounts workbook
    If Dir("C:\Docs\Account.xlsx") = "" Then
        Err.Raise ERROR_NO_ACCOUNTS, "UsingErr" _
                , "There are no accounts present for this month."
    End If

    ' UNEXPECTED ERROR - cannot be handled by the code
    ' If cell B3 contains text we will get a type mismatch error
    Dim total As Long
    total = Sheet1.Range("B3")
    
    
    ' continue on and read accounts
    
End Sub

This is a nice way of implementing error handling because

• We don’t need to add error handling code to every sub.
• If an error occurs then VBA exits the application gracefully.

A Complete Error Handling Strategy

The above strategy has one major drawback. It doesn’t provide any information about the error. It is better than having no strategy as it prevents the application crashing. But that is the only real benefit.

VBA doesn’t fill Err.Source with anything useful so we have to do this ourselves.

In this section, I am going to introduce a more complete error strategy. I have written two subs that perform all the heavy lifting so all you have to do is add them to your project.

The purpose of this strategy is to provide you with the Stack* and line number when an error exists.

*The Stack is the list of sub/functions that were currently in use when the error occurred.

This is our strategy

1. Place error handling in all the subs.
2. When an error occurs, the error handler adds details to the error and raises it again.
3. When the error reaches the topmost sub it is displayed.

We are simply “bubbling” the error to the top. The following diagram shows a simple visual of what happens when an error occurs in Sub3

The only messy part to this is formatting the strings correctly. I have written two subs that handle this, so it is taken care of for you.

There are the two helper subs, RaiseError and DisplayError. You can download the library below:

An Example of using this strategy

Here is a simple coding example that uses these subs. In this strategy, we don’t place any code in the topmost sub. We only call subs from it.

' https://excelmacromastery.com/
Sub Topmost()

    On Error Goto EH
    
    Level1

Done:
    Exit Sub
EH:
    DisplayError Err.source, Err.Description, "Module1.Topmost", Erl
End Sub

Sub Level1()

    On Error Goto EH
    
    Level2

Done:
    Exit Sub
EH:
   RaiseError Err.Number, Err.source, "Module1.Level1", Err.Description, Erl
End Sub

Sub Level2()

    On Error Goto EH
    
    ' Error here
    Dim a As Long
    a = "7 / 0"

Done:
    Exit Sub
EH:
    RaiseError Err.Number, Err.source, "Module1.Level2", Err.Description, Erl
End Sub

The result looks like this:

If your project has line numbers the result will include the line number of the error:

Error Handling in a Nutshell

• Error Handling is used to handle errors that occur when your application is running.
• You write specific code to handle expected errors. You use the VBA error handling statement On Error GoTo [label] to send VBA to a label when an unexpected error occurs.
• You can get details of the error from Err.Description.
• You can create your own error using Err.Raise.
• Using one On Error statement in the top most sub will catch all errors in subs that are called from here.
• If you want to record the name of the Sub with the error, you can update the error and rethrow it.
• You can use a log to record information about the application as it is running.

What’s Next?

Free VBA Tutorial If you are new to VBA or you want to sharpen your existing VBA skills then why not try out the The Ultimate VBA Tutorial.

Related Training: Get full access to the Excel VBA training webinars and all the tutorials.

(NOTE: Planning to build or manage a VBA Application? Learn how to build 10 Excel VBA applications from scratch.)

Two main purposes for error handling:

1. Trap errors you can
   predict but can’t control the user
   from doing (e.g. saving a file to a
   thumb drive when the thumb drives
   has been removed)
2. For unexpected errors, present user with a form
   that informs them what the problem
   is. That way, they can relay that
   message to you and you might be able
   to give them a work-around while you
   work on a fix.

So, how would you do this?

First of all, create an error form to display when an unexpected error occurs.

It could look something like this (FYI: Mine is called frmErrors):

Notice the following labels:

• lblHeadline
• lblSource
• lblProblem
• lblResponse

Also, the standard command buttons:

• Ignore
• Retry
• Cancel

There’s nothing spectacular in the code for this form:

Option Explicit

Private Sub cmdCancel_Click()
  Me.Tag = CMD_CANCEL
  Me.Hide
End Sub

Private Sub cmdIgnore_Click()
  Me.Tag = CMD_IGNORE
  Me.Hide
End Sub

Private Sub cmdRetry_Click()
  Me.Tag = CMD_RETRY
  Me.Hide
End Sub

Private Sub UserForm_Initialize()
  Me.lblErrorTitle.Caption = "Custom Error Title Caption String"
End Sub

Private Sub UserForm_QueryClose(Cancel As Integer, CloseMode As Integer)
  'Prevent user from closing with the Close box in the title bar.
    If CloseMode <> 1 Then
      cmdCancel_Click
    End If
End Sub

Basically, you want to know which button the user pressed when the form closes.

Next, create an Error Handler Module that will be used throughout your VBA app:

'****************************************************************
'    MODULE: ErrorHandler
'
'   PURPOSE: A VBA Error Handling routine to handle
'             any unexpected errors
'
'     Date:    Name:           Description:
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
'03/22/2010    Ray      Initial Creation
'****************************************************************
Option Explicit

Global Const CMD_RETRY = 0
Global Const CMD_IGNORE = 1
Global Const CMD_CANCEL = 2
Global Const CMD_CONTINUE = 3

Type ErrorType
    iErrNum As Long
    sHeadline As String
    sProblemMsg As String
    sResponseMsg As String
    sErrorSource As String
    sErrorDescription As String
    iBtnCap(3) As Integer
    iBitmap As Integer
End Type

Global gEStruc As ErrorType
Sub EmptyErrStruc_S(utEStruc As ErrorType)
  Dim i As Integer
    
  utEStruc.iErrNum = 0
  utEStruc.sHeadline = ""
  utEStruc.sProblemMsg = ""
  utEStruc.sResponseMsg = ""
  utEStruc.sErrorSource = ""
  For i = 0 To 2
    utEStruc.iBtnCap(i) = -1
  Next
  utEStruc.iBitmap = 1

End Sub
Function FillErrorStruct_F(EStruc As ErrorType) As Boolean
  'Must save error text before starting new error handler
  'in case we need it later
  EStruc.sProblemMsg = Error(EStruc.iErrNum)
  On Error GoTo vbDefaultFill

  EStruc.sHeadline = "Error " & Format$(EStruc.iErrNum)
  EStruc.sProblemMsg = EStruc.sErrorDescription
  EStruc.sErrorSource = EStruc.sErrorSource
  EStruc.sResponseMsg = "Contact the Company and tell them you received Error # " & Str$(EStruc.iErrNum) & ". You should write down the program function you were using, the record you were working with, and what you were doing."
  
   Select Case EStruc.iErrNum
       'Case Error number here
       'not sure what numeric errors user will ecounter, but can be implemented here
       'e.g.
       'EStruc.sHeadline = "Error 3265"
       'EStruc.sResponseMsg = "Contact tech support. Tell them what you were doing in the program."

     Case Else
       
       EStruc.sHeadline = "Error " & Format$(EStruc.iErrNum) & ": " & EStruc.sErrorDescription
       EStruc.sProblemMsg = EStruc.sErrorDescription
      
   End Select
   
   GoTo FillStrucEnd
   
vbDefaultFill:

  'Error Not on file
  EStruc.sHeadline = "Error " & Format$(EStruc.iErrNum) & ": Contact Tech Support"
  EStruc.sResponseMsg = "Contact the Company and tell them you received Error # " & Str$(EStruc.iErrNum)
FillStrucEnd:

  Exit Function

End Function
Function iErrorHandler_F(utEStruc As ErrorType) As Integer
  Static sCaption(3) As String
  Dim i As Integer
  Dim iMCursor As Integer
  
  Beep

  'Setup static array
  If Len(sCaption(0)) < 1 Then
    sCaption(CMD_IGNORE) = "&Ignore"
    sCaption(CMD_RETRY) = "&Retry"
    sCaption(CMD_CANCEL) = "&Cancel"
    sCaption(CMD_CONTINUE) = "Continue"
  End If

  Load frmErrors
  
  'Did caller pass error info?  If not fill struc with the needed info
  If Len(utEStruc.sHeadline) < 1 Then
    i = FillErrorStruct_F(utEStruc)
  End If

  frmErrors!lblHeadline.Caption = utEStruc.sHeadline
  frmErrors!lblProblem.Caption = utEStruc.sProblemMsg
  frmErrors!lblSource.Caption = utEStruc.sErrorSource
  frmErrors!lblResponse.Caption = utEStruc.sResponseMsg
  
  frmErrors.Show
  iErrorHandler_F = frmErrors.Tag   ' Save user response
  Unload frmErrors                  ' Unload and release form

  EmptyErrStruc_S utEStruc          ' Release memory

End Function

You may have errors that will be custom only to your application. This would typically be a short list of errors specifically only to your application.
If you don’t already have a constants module, create one that will contain an ENUM of your custom errors. (NOTE: Office ’97 does NOT support ENUMS.). The ENUM should look something like this:

Public Enum CustomErrorName
  MaskedFilterNotSupported
  InvalidMonthNumber
End Enum

Create a module that will throw your custom errors.

'********************************************************************************************************************************
'    MODULE: CustomErrorList
'
'   PURPOSE: For trapping custom errors applicable to this application
'
'INSTRUCTIONS:  To use this module to create your own custom error:
'               1.  Add the Name of the Error to the CustomErrorName Enum
'               2.  Add a Case Statement to the raiseCustomError Sub
'               3.  Call the raiseCustomError Sub in the routine you may see the custom error
'               4.  Make sure the routine you call the raiseCustomError has error handling in it
'
'
'     Date:    Name:           Description:
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
'03/26/2010    Ray       Initial Creation
'********************************************************************************************************************************
Option Explicit
Const MICROSOFT_OFFSET = 512 'Microsoft reserves error values between vbObjectError and vbObjectError + 512
'************************************************************************************************
'  FUNCTION:  raiseCustomError
'
'   PURPOSE:  Raises a custom error based on the information passed
'
'PARAMETERS:  customError - An integer of type CustomErrorName Enum that defines the custom error
'             errorSource - The place the error came from
'
'   Returns:  The ASCII vaule that should be used for the Keypress
'
'     Date:    Name:           Description:
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'03/26/2010    Ray       Initial Creation
'************************************************************************************************
Public Sub raiseCustomError(customError As Integer, Optional errorSource As String = "")
  Dim errorLong As Long
  Dim errorDescription As String
  
  errorLong = vbObjectError + MICROSOFT_OFFSET + customError
  
  Select Case customError
  
    Case CustomErrorName.MaskedFilterNotSupported
      errorDescription = "The mask filter passed is not supported"
      
    Case CustomErrorName.InvalidMonthNumber
      errorDescription = "Invalid Month Number Passed"
      
    Case Else
      errorDescription = "The custom error raised is unknown."
      
  End Select
  
  Err.Raise errorLong, errorSource, errorDescription
  
End Sub

You are now well equipped to trap errors in your program. You sub (or function), should look something like this:

Public Sub MySub(monthNumber as Integer)
  On Error GoTo eh  
  
  Dim sheetWorkSheet As Worksheet
  
  'Run Some code here
  
  '************************************************
  '*   OPTIONAL BLOCK 1:  Look for a specific error
  '************************************************
  'Temporarily Turn off Error Handling so that you can check for specific error
  On Error Resume Next
  'Do some code where you might expect an error.  Example below:
  Const ERR_SHEET_NOT_FOUND = 9 'This error number is actually subscript out of range, but for this example means the worksheet was not found
  
  Set sheetWorkSheet = Sheets("January")
  
  'Now see if the expected error exists
  
  If Err.Number = ERR_SHEET_NOT_FOUND Then
    MsgBox "Hey!  The January worksheet is missing.  You need to recreate it."
    Exit Sub
  ElseIf Err.Number <> 0 Then
    'Uh oh...there was an error we did not expect so just run basic error handling 
    GoTo eh
  End If
  
  'Finished with predictable errors, turn basic error handling back on:
  On Error GoTo eh
  
  '**********************************************************************************
  '*   End of OPTIONAL BLOCK 1
  '**********************************************************************************
  
  '**********************************************************************************
  '*   OPTIONAL BLOCK 2:  Raise (a.k.a. "Throw") a Custom Error if applicable
  '**********************************************************************************
  If not (monthNumber >=1 and monthnumber <=12) then
    raiseCustomError CustomErrorName.InvalidMonthNumber, "My Sub"
  end if
  '**********************************************************************************
  '*   End of OPTIONAL BLOCK 2
  '**********************************************************************************
  
  'Rest of code in your sub
  
  goto sub_exit

eh:
  gEStruc.iErrNum = Err.Number
  gEStruc.sErrorDescription = Err.Description
  gEStruc.sErrorSource = Err.Source
  m_rc = iErrorHandler_F(gEStruc)
  
  If m_rc = CMD_RETRY Then
    Resume
  End If

sub_exit:
  'Any final processing you want to do.
  'Be careful with what you put here because if it errors out, the error rolls up.  This can be difficult to debug; especially if calling routine has no error handling.
  
  Exit Sub 'I was told a long time ago (10+ years) that exit sub was better than end sub...I can't tell you why, so you may not want to put in this line of code.  It's habit I can't break :P
End Sub

A copy/paste of the code above may not work right out of the gate, but should definitely give you the gist.