I've found solution to my problem in this thread : HOW-TO Use the FOR command (+ other missing DOS commands) & automate ISO mounting. Thanks guys.

Hello, I am trying to write a batch script that loops over all file in the current directory and performs some operation on thatm, and I want to use for command to do the looping. But DosBox says for is an illegal command. After a quick googling I found out, for is not a supported command in DosBox. …