CustomTween.prototype = new Tween();
CustomTween.prototype.constructor = Tween;
CustomTween.superclass = Tween.prototype;

function CustomTween(fnc, from, to, duration, tweenType) {
    this.onMotionChanged = function(evt) { fnc(evt.target._pos) }; 
	this.init(new Object(),'x',tweenType,from,to,duration);
}