To do that, you have to set up a timer function that will "check" every window you have open to see whether or not anything - which includes x-pos, y-pos, width, height, whether or not the window is even open, and (if I'm not mistaken) mIRC's appstate - has changed since the last check.
Its plainly inefficient, IMO. Testing every single window for changes takes time. Not too much time, but it would still be more efficient if mIRC reported it instead.
Then there's the reality that while a timer function would work appropriately, it would not 'look' nice. If you have a delay of five seconds, then there's a chance the update might not happen for five seconds. If you have a delay of one second, you have mostly-useless checks placing a bothersome load on the system.