Which forum is it? I mean the link...
I don't think it should be overly hard to do, but the problem is I have nothing to test on...atleast not without pissing off owners of a forum if my socketed posts would turn out somewhere else :P
Btw are you always going to want to reply in a certain restricted thread, or is it more like in a restricted forum which can have multiple threads, and you want to be able to make a thread?