XL: How to Force Macro Code to Wait for Outside Procedure

• Microsoft Excel 97 for Windows
• Microsoft Excel for Windows 95, version 7.0
• Microsoft Excel for Windows, versions 5.0

SUMMARY

In the versions of Microsoft Excel listed at the beginning of this article, you can use a Visual Basic for Applications macro to run other Windows and MS-DOS applications and procedures. The macro code in Microsoft Excel continues to execute even after the external procedure has been initiated. You must write code to handle delays if Microsoft Excel is to wait for the output from the outside procedure.

MORE INFORMATION

Microsoft provides examples of Visual Basic for Applications 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. The Visual Basic procedures in this article are provided 'as is' and Microsoft does not guarantee that they can be used in all situations. While Microsoft support engineers can help explain the functionality of a particular macro, they will not modify these examples to provide added functionality, nor will they help you construct macros to meet your specific needs. If you have limited programming experience, you may want to consult one of the Microsoft Solution Providers. Solution Providers offer a wide range of fee-based services, including creating custom macros. For more information about Microsoft Solution Providers, call Microsoft Customer Information Service at (800) 426-9400.

Creating the Module

Before you use the examples in this article, perform the following steps:

1. Open a new workbook.

2. Insert a new module sheet. To do this in Microsoft Excel 97, point to Macro on the Tools menu, and click Visual Basic Editor. In the Visual Basic Editor, click Module on the Insert menu.

   In Microsoft Excel 7.0, point to Macro on the Insert menu and click Module.

3. Type the example macro code in the module sheet.

Example 1: Creating a Flag

For the macro code in example 1 to work correctly, you need to make your custom application create a flag when it has completed execution. In the following example your custom application should create a text file at C:\Flag.txt to act as this flag.

   Sub Appacttest()

      ' Checks to see if Flag.txt already exists.
      FindIt = Dir("C:\Flag.txt")

      ' If the file Flag.txt has been found then delete it.
      If  Not Len(FindIt) = 0  Then
         Kill "C:\Flag.txt"
      End If

      ' Sets Myapp variable equal to the Shell statement.
      Myapp = Shell("C:\Custom.exe", 1)

      ' Executes the shell statement.
      AppActivate Myapp

      ' Checks to see if Flag.txt can be found yet.
      FindIt = Dir("C:\Flag.txt")

   ' The following While Wend loop will keep Microsoft Excel "suspended"
   ' until the custom application is complete. This will occur while the
   ' length of the FindIt variable is equal to 0. Microsoft Excel will
   ' remain busy until it finds the file Flag.txt, thus making the length
   ' of FindIt > 0 and ending the loop.

      ' Check to see if the length of FindIt variable is equal to 0
      ' chars.
      While Len(FindIt) = 0

      ' Continue to check if flag was created yet.
      FindIt = Dir("C:\Flag.txt")

      Wend

      ' Continue with more code if needed.
   End Sub

Example 2: Using an Intermediate File to Avoid a Sharing Violation

This example uses an intermediate file to allow the MS-DOS DIR command to complete and close the output before Microsoft Excel attempts to open it. If this method were not used, the Workbooks.Open method would generate a sharing violation by attempting to open the output while it was still being written.

While the example below illustrates one use of this procedure, you could apply the same method to any MS-DOS or Windows application that generates an output file that can be read by Microsoft Excel.

   Sub WaitForOutput()

   If Len(Dir("c:\output.txt")) > 0 Then Kill "c:\output.txt"
   If Len(Dir("c:\temp.txt")) > 0 Then Kill "c:\temp.txt"
   ' Test for previous files and delete them.

   Shell "command.com /c dir c:\windows\*.* >c:\temp.txt"
   ' Run MS-DOS DIR command to pipe the directory of
   ' c:\windows into an intermediate text file, temp.txt.

   On Error Resume Next
   ' Set error condition to skip to the next line,
   ' for Name statement below.

   Do Until Len(Dir("c:\output.txt")) > 0
   ' Begin a loop to test for final output file, output.txt.

      Name "c:\temp.txt" As "c:\output.txt"
      ' Attempt to rename temp.txt to output.txt;
      ' will fail until temp.txt is closed

      DoEvents
      ' Allow for other processes, including the shelled
      ' procedure above, to continue in the background Loop
   'End the loop

   Workbooks.Open ("c:\output.txt")
   ' Open the resulting text file, output.txt, into an Excel worksheet.

   End Sub

REFERENCES

For additional information, please see the following article(s) in the Microsoft Knowledge Base:

   ARTICLE-ID: Q129796
   TITLE     : How to Determine When a Shelled 32-bit Process Has
               Terminated

   ARTICLE-ID: Q96844
   TITLE     : How to Determine When a Shelled 16-bit Process Has
               Terminated

   Shell

For more information about the Shell function in Microsoft Excel 7.0, click Answer Wizard on the Help menu and type:

   tell me about the Shell function