Actually if you launch the batch file from the MAS90 folder and put a /s at the end, it seems to work.
To test use the dir command instead of del.
e.g. dir *wrk*0*.m4t /s
But if you do launch it from the MAS90 folder, you may wipe out some files you might want. Note the sy_journalerrorlog toward the middle. Other than that, it seems to work with only one line.