Not sure if this is what you are looking for but this is what I currently use in my script and it uses two different sounds. One sound plays when the person first private message's you (eg: incoming private message) and a second one for everytime they type in the query window (eg: beep). Works very well and it also only plays the sounds if the window is not active except when the query window is active but mirc is minimized then the sound will alert when something is typed.
