XL5: Incorrect Results or Crash Returning Data Using API

The information in this article applies to:

• Microsoft Excel for Windows, version 5.0

SYMPTOMS

In Microsoft Excel version 5.0, if you create a Visual Basic, Applications Edition, procedure that uses a Microsoft Windows API (application programming interface) Library to return a value, an incorrect value may be returned, or your system may hang (stop responding) if you do not specify the data type of the value returned by the function.

CAUSE

This behavior occurs because when you do not declare the data type of the return value of a function, it is assumed to be of Variant data type. For example, if the return value is an integer, and you do not declare the return value as an integer, the value is assumed to be of Variant data type which causes an incorrect value to be returned or may even cause your system to hang.

WORKAROUND

To avoid returning an incorrect value, or having your system crash when you use a Microsoft Windows API function in a Visual Basic function, declare the return type of the function when you declare the function. For example, the following statement explicitly declares the return value of the GetSystemMetrics function as an Integer type:

   Declare Function GetSystemMetrics Lib "User" (ByVal n As Integer) As
      Integer

Microsoft provides examples of Visual Basic procedures for illustration only, without warranty either expressed or implied, including but not limited to the implied warranties of merchantability and/or fitness for a particular purpose. This Visual Basic procedure is provided 'as is' and Microsoft does not guarantee that it can be used in all situations. Microsoft does not support modifications of this procedure to suit customer requirements for a particular purpose. Note that a line that is preceded by an apostrophe introduces a comment in the code--comments are provided to explain what the code is doing at a particular point in the procedure. Note also that an underscore character (_) indicates that code continues from one line to the next. You can type lines that contain this character as one logical line or you can divide the lines of code and include the line continuation character. For more information about Visual Basic for Applications programming style, see the "Programming Style in This Manual" section in the "Document Conventions" section of the "Visual Basic User's Guide."

REFERENCES

For more information about the Declare statement, choose the Search button in Help and type:

    Declare