public function TimerExample() {
    timer = new Timer(30);
    timer.addEventListener("timer", timerHandler);
    timer.start();
}
private var timer:Timer;
private var endValue:int  = 200;
private var value:int = 100;
private var step:int = 20;

public function timerHandler(event:TimerEvent):void {
    //trace("timerHandler: " + event);
    value += step;
    if ( value >= endValue )
    {
        timer.stop();
        timer.removeEventListener("timer", timerHandler);
    }
}