bring button (and pop up) to front on roll over

I am using button symbols to create pop ups on rollover (by sticking the pop up box in their rollover state)

However I need a way to bring the buttons to the front when I rollover them because the pop  up overlap the other buttons.

Irealise this question has been asked before but I’m very new to as3 and I’m having difficulty adapting the answers to my code.

I greatly appreciate any help

Ben

var buttons:Array = [btn1,btn2];

function moveFront(event:MouseEvent):void {

                // move to front code

}

for(var i:uint = 0; i<buttons.length; i++) {

                buttons.addEventListener(MouseEvent.ROLL_OVER, moveFront);

}