Banning users from each other's thread..

[magnus]

We have a few users on our forum who just can't seem to play nice, and being paying members, we'd prefer not to ban them. However, I've wondered if it's possible to device a hack to ban user {x} from any thread started by user {y} and vice versa. Or perhaps each user has an input field which contains a list of users that it checks against, if the thread starter matches their list, they cannot reply.

Or, perhaps, someone has a better solution? (other than banning, lol)