ActionScript 2.0 :: Continue Zooming In For As Long As The Mouse Is Over The Button

i've made a button that zooms into a movie clip on a rollover, but it on moves it a certain amount each time you rollover the button. code below: on (rollOver){

_root.Mypic._width += 5;
_root.Mypic._height += 5;
}

wot i want it to do is to continue zooming in for as long as the mouse is over the button, is there anyway i can change the code to zoom in at the same amount but do it continuously until the mouse is moved off the button. Also is there anyway that i can set it so that the zoom stops at a certain percentage, i.e. it only zooms in so much and then stops. What i mean is that the user can zoom in but the picture will only zoom in to say 200% of the original size.