[kh99]

I don't know if there's an existing mod, but it wouldn't be a very difficult plugin (I know, it's easy for me to say that...).

Anyway, using hook newpost_process you could check $foruminfo['forumid'] and $post['title'], and if it's not acceptable call $dataman->error('errorphrase'); (where errorphrase is the varname of a phrase with your error message, which you'd have to create in the Phrase Manager).