Need help with Flex 3 Tile

hi I have made one Tile and add Image with AS3 in it I want to make to have on sth like oRollOver ? possilble? how?

here is how I add images:
private function addToGAllery():void {
var i:int;
var iNum:int = galleryAllImageCollection.length;
for (i=0; i<iNum;i++) {
var imageTag:Image = new Image();
imageTag.source = galleryAllImageCollection*.thumbnail; = galleryAllImageCollection*.id;