>I've been calling a form (called PROGRESS) from within a programme of mine, and I would like to kill only this form at the end of the programme.

Progress.Release()

I would use the NAME cluase to make sure its fine:

do form progress.scx name loProgress
*Stuff
if loProgress.QueryUnload()
     loProgress.Release()
endif

BTW, The QueryUnload isn't default behavior, but its a default event.