Adding a cross fade to this script

1

hi below is my code

could anybody show me how to edit it, to make it cross fade instead of fade in/out?

Thankyou

import fl.transitions.Tween;
import fl.transitions.TweenEvent;
import fl.transitions.easing.*;
var bg1Tween:Tween = new Tween (bgs_mc.bg1_mc, "alpha", None.easeInOut, 0 , 1 , 1 , true );
bg1Tween.stop();
bg1Tween.addEventListener(TweenEvent.MOTION_FINISH,fadeOutbg);
var bg2Tween:Tween = new Tween (bgs_mc.bg2_mc, "alpha", None.easeInOut, 0 , 1 , 1 , true );
bg2Tween.stop();
var bg3Tween:Tween = new Tween (bgs_mc.bg3_mc, "alpha", None.easeInOut, 0 , 1 , 1 , true);
bg3Tween.stop();
bgs_mc.bg1_mc.nextTween = bg2Tween;
bgs_mc.bg2_mc.nextTween = bg3Tween;
bgs_mc.bg3_mc.nextTween = bg1Tween;
setTimeout (bg1Tween.start, 1000);
function fadeOutbg(event:TweenEvent) {
event.target.removeEventListener(TweenEvent.MOTION_FINISH, fadeOutbg);
event.target.addEventListener(TweenEvent.MOTION_FINISH, startNextbg);
event.target.begin = 1;
event.target.finish = 0;
setTimeout (event.target.start, 6000);
}
function startNextbg(event:TweenEvent) {
event.target.removeEventListener(TweenEvent.MOTION_FINISH, startNextbg);
event.target.obj.nextTween.addEventListener(TweenEvent.MOTION_FINISH, fadeOutbg);
event.target.obj.nextTween.begin = 0;
event.target.obj.nextTween.finish = 1;
setTimeout (event.target.obj.nextTween.start, 1000);
}