locking the Supernote position relative to a nav button

Looking for a script that will show a hidden layer (300px high) right above a navigation button (40px high) on Mouseover. Button link is down the page about 500px. This Supernote is a very elegant solution, but I can't figure out how to get that note to lock in place independent of the browser window size. The layer moves around depending on weather I resize the window or scroll down, etc. It only positions over the button when the browser window is sufficiently long enough to accomodate about twice the height of the hidden layer -- at about 800px tall. Shorter than that and my layer starts moving north with it. Probably something simple but I've tweaked the hell out of it and can't win.