As a note, it wouldn't be too much trouble to put a dialog or picwin "button" over mIRC that will check all of the words in your editbox using an online dictionary. It shouldn't even be that difficult. For that matter, you could just check it by running the text through Google's search and see if it pops up a "did you mean" link, which would mean a single search rather than searching every word in your editbox.
I don't think I'd have it do this automatically using on INPUT just for speed issues and you probably don't need every line to be checked... only ones with words you're not sure of. I think it would be better to have a button that checks your current line before you send it.
