попробуй так
Код AS3:
import flash.display.Sprite;
import flash.text.*;
stage.addEventListener(MouseEvent.CLICK,addBall);
function addBall(e:MouseEvent):void{
var ball:Ball=new Ball();
addChild(ball);
ball.x=mouseX;
ball.y=mouseY;
myText.text= Ball.allBalls.length.toString();
}