You can create a file in case of error and than check for it existence in the VFP app.

* Batch file
ECHO File blblbla is in use! > C:\temp\whatever.txt
...
* VFP
IF FILE("C:\temp\whatever.txt")
  = messagebox("Blablabla")
  ERASE ("C:\temp\whatever.txt")
ENDIF

>
>This will let me know a file is in use in the command window alright. But what if I run the batch ouside of the command window. How will I know it failed?