I know of the notify list that comes with mIRC, but for roleplaying reasons, I have a friend who changes his nick to various things. Instead of adding all the names he uses, could someone make me a simple script that will notify me when someone matching his IP address comes on?

And if you could, would I put just the number, or the whole address?

From the help file:

Note: Some IRC networks might let you use a full address instead of just a nickname, the only way to see if it works is to try it out.