Easy.

Code:
on *:join:#Channel: {
  if ($nick == Nick1) { /msg $chan Hello. }
  if ($nick == Nick2) { /msg $chan Different sentence. }
}


Heh, I was a bit surprised when I saw your nick. One of the forum moderators here, Cobra^, is owner of a #mIRC channel on Webnet (split from Dalnet a long time ago) and one of his ops was a guy named Wall. Mus not be you.