>Hello,
>
>A couple of times I received email error message pointing to the fact that
>'ShellExecute.prg' does not exist.
>
>In my code I do have calls to execute the ShellExecute (Windows API function) when printing PDF documents.
>So, the ShellExecute is outside of what my program created.
>
>What would cause this error?
>
>TIA

The command

  DECLARE INTEGER ShellExecute IN "Shell32.dll" ;
   INTEGER HWND, ;
   STRING lpVerb, ;
   STRING lpFile, ;
   STRING lpParameters, ;
   STRING lpDirectory, ;
   LONG nShowCmd

is not executed before

ShellExecute( ....

or CLEAR DLLS is executed between

Possibly a third party tool clears the DLL, so it is good practice to have the DLL call like

ShellExecute( ....

FUNCTION  ShellExecute (tHWND, tlpVerb, tlpFile, tlpParameters, tlpDirectory, tnShowCmd)

 DECLARE INTEGER ShellExecute IN "Shell32.dll" ;
    INTEGER HWND, ;
    STRING lpVerb, ;
    STRING lpFile, ;
    STRING lpParameters, ;
    STRING lpDirectory, ;
    LONG nShowCmd

 RETURN  ShellExecute (tHWND, tlpVerb, tlpFile, tlpParameters, tlpDirectory, tnShowCmd )
Endfunc

Due to the way VFP calls functions, the FUNCTION is called only if the DLL is not declared. So if cleared, it's auto declared again.

HTH
Lutz