WhileMouseOn()
This function can be called after a ONBUTTONOVER event occurred. If you call this function, Hollywood will wait until the user moves the mouse out of the button it is currently over. This is useful when you want to display a brush when the mouse is over a button (hover effect).
This function is optional after an ONBUTTONOVER event (other than the WhileMouseDown() function which is required after a ONBUTTONCLICK event!)