No automatic type coercion between variable types

View products that this article applies to.

This article was previously published under Q213562

SYMPTOMS

When you run a Microsoft Visual Basic for Applications macro in Microsoft Excel, you may receive the following error message:

Compile error:
ByRef argument type mismatch

Back to the top

CAUSE

This problem may occur if all of the following conditions are true:

Within your code, one macro is executing another macro.
The first macro is attempting to pass a value to the second macro. The value in question is an element of an array declared as type Variant.
The second macro is set up to accept a value from the first macro, but of a type other than Variant (Integer or Long, for example).

This behavior is by design of Microsoft Excel. The behavior demonstrated by versions of Microsoft Excel earlier than Excel 97 is actually incorrect.

Back to the top

Microsoft provides programming examples for illustration only, without warranty either expressed or implied. This includes, but is not limited to, the implied warranties of merchantability or fitness for a particular purpose. This article assumes that you are familiar with the programming language that is being demonstrated and with the tools that are used to create and to debug procedures. Microsoft support engineers can help explain the functionality of a particular procedure, but they will not modify these examples to provide added functionality or construct procedures to meet your specific requirements. The following workarounds assume that you have a Visual Basic module that contains two macros:

   Sub Macro1()
       Dim X As Variant
       X = ActiveWorkbook.Sheets("Sheet1").Range("A1:A5")
       Macro2 X(1, 1)          'X is an array of type Variant...
   End Sub

   Sub Macro2(Y As Integer)    '...but Macro2 expects an Integer.
       MsgBox Y
   End Sub

When you run these macros, the first macro (Macro1) initializes an array named X, populates the array, and then sends a value from the array to the second macro (Macro2). Macro2 then displays the value in a message box. If you run Macro1 without applying any of the following workarounds, you will receive the error message described in the "Symptoms" section.

Back to the top

Method 1

To prevent the problem from occurring, change how the second macro (Macro2) accepts values. In this case, change the second macro as follows:

   Sub Macro2(Y As Variant)    'Y is now a Variant, not an Integer.
       MsgBox Y
   End Sub

This eliminates the problem because you are sending an element from an array of type Variant to a variable of type Variant.

Back to the top

Method 2

A second way to prevent the problem from occurring is to convert the value to an Integer as you pass it to the second macro using the CInt function.

   Sub Macro1()
       Dim X As Variant
       X = ActiveWorkbook.Sheets("Sheet1").Range("A1:A5")
       Macro2 CInt(X(1, 1))  'Convert Variant X(1, 1) using CInt
   End Sub

   Sub Macro2(Y As Integer)  'Macro2 expects an Integer.
       MsgBox Y
   End Sub

Back to the top

Method 3

Another way to prevent the problem from occurring is to dimension a second variable in the first macro. This second variable should be of the same type as the value accepted by the second macro. Copy the value from the array into the second variable, and then send it to the second macro. For example:

   Sub Macro1()
       'Z is the second variable. It is an Integer, just like Y.
       Dim X As Variant, Z As Integer

       X = ActiveWorkbook.Sheets("Sheet1").Range("A1:A5")
       Z = X(1, 1) 'Get the value from the array and put it in Z.
       Macro2 Z    'This works correctly.

   End Sub

Because Z is an integer, the value of Z is received by Macro2 (which expects an integer) correctly.

Back to the top

MORE INFORMATION

In versions of Microsoft Excel earlier than Excel 97, you can pass a value from an element in an array of type Variant in one function, to a variable of another type in another function. This is called "automatic type coercion," because the value passed between functions is being forced (coerced) to switch from one type (Variant) to another type (Integer, for example).

Microsoft Excel 2000 does not support automatic type coercion. Because of this, you may need to ensure that your macros consistently use the same types of variables when passing values from macro to macro.

Back to the top