I believe there is none working example of WM_MOUSELEAVE notification ( I could be wrong ), using TrackMouseEvent, on this Forum.
I've had some serious trouble some time to make it work.
I believe someone will use it one day :]
Global $is_tracking = False
Global $iteration = 1 ; Just to recognize different ConsoleWrite's in spammed console
Global $hGui = GUICreate('')
Global $sTrackMouseEvent = DllStructCreate('dword;dword;hwnd;dword') ; Creating TRACKMOUSEEVENT Structure