how to limit some files extensions in proftpd

I'm using debian etch and proftpd (and ispconfig)

I want to be able to limit certains files extensions in the upload or rename process, for example .exe or .mp3 upload or rename (or any command like this) would be forbidden.

is there a way to do this ?

if yes, is there a way to do this for certain user or directory only ?

Thanks

 

It's probably the right option, thanks