ActionScript 3.0 :: Open New Window With Enlarged Image On Button Click

I just started out using autoscript 3.0. What I want is that when I click a button (with an image inside) it opens a new window with an enlargement of that image. I've already done the following:
1. Create new button
2. Set it's instance nam to appinvent_btn
3. Created new action layer.
4. Set up the following script in actionscript 3.0

appinvent_btn.addEventListener(MouseEvent.MOUSE_DO WN, mouseDownHandler);
function mouseDownHandler(event:MouseEvent):void {
navigateToURL(new URLRequest("???????????????????????????"));
}