ask an admin to do it
they get everyone's ip who comes here and signs up. if it is another member holding a grudge and using another screen name to attack you then a match will be found.
well unless they know how to proxy that is, and i assume that if you bann that ip it would also bann that other screen name they may be using. lets say BW is the attacker. if you start comparing ip's you would match his to that other guy. and if you were to bann that guys ip it would also bann BW from here.
so if it is another member doing it then it is as simple as that to catch them