Stop yoyo or reverse tween

programming flash
1

I want the tween to end when the alpha and the _x tween go back to the beginning

here is my code

import mx.transitions.Tween;
import mx.transitions.easing.*;
var xScaleT:Tween = new Tween(kText, “_x”, Back.easeOut, 0, 476.7, 3, true);
var alpha:Tween = new Tween(kText, “_alpha”, Regular.easeIn, 0, 100, 1, true);
xScaleT.onMotionFinished = function() {

this.yoyo();
alpha.yoyo();

};

I cant stop the code without interuppting the reversal of the tween.