I assume this is out of the question... Identify users from other boards cookies?

[South Fork]

Trying to figure out if it's possible to check another boards cookie. The reason is to identify a member from another board, one who you know and have banned off your board. Occationally I've seen them come back on with various ID's using non-descript yahoo / hotmail accts, and post only with the intent of stirring up trouble. I'm looking for a tool that'll make identifying them easier.

I'm assuming the answer to this is no but thought I'd ask. The reason for the query / request is that I just found a user that had been banned had six other accounts and used them occationally to make my job a little harder.