[Волгоградец]

import mx.transitions.Tween;

class Test
{
	
	private var _mc:MovieClip;
	private var clip:MovieClip;
	
	public function Test (mc:MovieClip)
	{
		_mc = mc;
		clip = _mc.createEmptyMovieClip("clip", 0);
		clip.beginFill(0xFF0000);
		clip.moveTo(0, 0);
		clip.lineTo(20, 0);
		clip.lineTo(20, 20);
		clip.lineTo(0, 20);
		clip.lineTo(0, 0);
		
		clip._y = 100;
	}
	
	public function follow ():Void
	{
		var myTween:Tween = new Tween(clip, "_x", mx.transitions.easing.None.easeNone,0, Stage.width, 100, false);
		myTween.onMotionFinished = function() {
			myTween.start();
		}
	}
}

Использовать:

var a:Test = new Test(_root);
a.follow();