Sadly this isn't really something you get to know unlesss your an ircop or for some reason the server lets you know about it.
Whois information comes straight from teh server unlike CTCP versions, pings, etc; so ordinarily you can't get this info.
I heard of one or two networks giving the raw on a whouis thingy to the everyday cahtter; but i can't fo r the life of me remember which ones.
