How to control nested MC created with addChild?

1

i tried a lot but couldn’t fix the problem…

why is the following code is not working?
(please see fla too)…

thanks a lot!

the code:


/*
i tried to create nested movieClip, and then to add it eventListener, and to it's nested mc too.
i can't control neither the "mySquare_mc" MovieClip, and neither it's nested MovieClip ("circle_mc")
while i'm trying to control the inner MC i get this Error:
"TypeError: Error #1009: Cannot access a property or method of a null object reference.
	at example_fla::MainTimeline/moveIt()"
	
what can be the problem?!

*/

import flash.events.MouseEvent;

var mySquare_mc:MovieClip = new sq();
mySquare_mc.name = "sq";
mySquare_mc.x = 20;
mySquare_mc.y = 20;
addChild(mySquare_mc);


var circle_mc:MovieClip = new cc();
circle_mc.x = 10;
circle_mc.y = 10;
mySquare_mc.addChild(circle_mc);

mySquare_mc.addEventListener(MouseEvent.CLICK,moveIt);

function moveIt(event:MouseEvent){
	mySquare_mc.x+=50;
	mySquare_mc.circle_mc.alpha-=0.1;
}

//this is not working too:

/*function moveIt(event:MouseEvent){
	mySquare_mc.x+=50;
	getChildByName("mySquare_mc").getChildByName("circle_mc").alpha-=0.1;
}*/