Yo,
You have either to write your own client  IRC, or to modify
the source Code
one of the most famous client IRC: ircII (I dunno the actual
release ... maybe 2.9.x).

If u dont have ircII, well it's not hard to find it on the
Net ...
For further info, check out www.2600.com and look for the
FAQ (even old ones)

Bye