He's asking for a way to script something in order to properly integrate with mIRC's existing features/UI. There's no reason to re-script channel favourites if the functionality exists.
That said, I'm sure Khaled looked at this request 8 months ago. It's probably somewhere on his todo list (or maybe not). Just because you ask for something does not mean it will be added, so in the meantime you *should* look at a completely scripted solution (as in, one without the existing favourites feature).