detecting mouseup ouside window

[y2k1981]

is it possible to detect a mouseup outside of the body, ie when the user brings the mouse up towards the toolbar? I'm creating a movable div and have tried several different options but none provide exactly what I need. I've tired event.clientX < 0 and I've tired adding an onmouseout to the bodytag but it's getting called every time I put the mouse over the div instead of just every time the mouse leaves the window. I can't understand this as this would actually suffice if it were only called when the mouse leaves the window.