Scaling a circle w/ as3

programming flash
1

I got the circle to scale up but need assistance to have the circle scale down after x amount of time. Would appreciate any help

import flash.display.MovieClip;
import fl.transitions.Tween;
import fl.motion.Tweenables;
import fl.transitions.easing.Strong;
import fl.transitions.easing.None;

var tweenScaleX : Tween;
var tweenScaleY : Tween;


function grow(mc : MovieClip) : void
{
    tweenScaleX = new Tween(mc, Tweenables.SCALE_X, None.easeNone, mc.scaleX, 3, 5, true);
    tweenScaleY = new Tween(mc, Tweenables.SCALE_Y, None.easeNone, mc.scaleY, 3, 5, true); 
}

grow(myCircle);