AS3 movieClip access to variables

Hi all,

Like everybody else I have been trying to get my head around Actionscript 3 and the way it works compared to Actionscript 2.
One thing I am having a major problem with, is accessing from one movie the variables of another movie.

In ActionScript 2 this problem could be solved like this:
_root.movieClip1.quantity = 10;
_root.movieClip2.quantity = 200;

If I was inside movieClip1 and I needed the quantity value from the movieClip2 I could say:
trace (_root.movieClip2.quantity);

In ActionScript 3 I have the following code that I am trying (and works fine):

package {
import flash.display.Sprite;
import flash.display.MovieClip;
import flash.events.Event;
import flash.events.MouseEvent;

public class test extends MovieClip {

public function test() {
init();
}

public function init():void {
var button1:MovieClip = new MovieClip();
var button2:MovieClip = new MovieClip();

button1.graphics.beginFill(0xFF0000);
button1.graphics.drawRect(100, 100, 100, 15);
button1.graphics.endFill();
button1.quantity = 10;

button2.graphics.beginFill(0xFF0000);
button2.graphics.drawRect(300, 100, 100, 15);
button2.graphics.endFill();
button2.quantity = 100;

addChild (button1);
addChild (button2);

button1.addEventListener(MouseEvent.CLICK, onOverButton1);
button2.addEventListener(MouseEvent.CLICK, onOverButton2);
}

public function onOverButton1(event:MouseEvent):void {
trace (event.currentTarget.quantity);
}

public function onOverButton2(event:MouseEvent):void {
trace (event.currentTarget.quantity);
}
}
}

What this does is just tracing the quantity variable for the movie clip you click on.

My question is what kind of code would I put in the onOverButton1 function to access the quantity variable of button2?