Please help rotationY

hello

i create stage Mouse Rotation Y is complete

and i want to put some easing on movieclip

this is my code

import flash.events.Event;
addEventListener(Event.ENTER_FRAME, onEnterFrame);
function onEnterFrame(event:Event):void
{
 bkgd.rotationY = (stage.mouseX - stage.stageWidth/2) * 0.1;
}

please help

thanks all people for help