If the compile step in the batch file returns a non-zero exitcode on failure, VBP will detect that (and fail the build) if you call it like
%DOSCMD% call "drive:\path\to\file.bat"
and you exit the batch file without executing other commands.
As far as forcing a failure, see this FAQ:
http://www.kinook.com/Forum/showthread.php?threadid=142