Okay, I will write this script since I want it to myself.
What annoys me is if someone parts the channels I'm in, then pms me. Then I have to scroll at what channels this person parted from. So storing the variables for an hour should do it. I've always wanted to write a script for that.
The only option is when a user parts/quits all channels you're in, mIRC removes them from your IAL. If there is a way to prevent that, that would be great. But I got no response.