Passing button X position


i´m using the code bellow to move a MC on buttons Click

import caurina.transitions.*;

button1.addEventListener (MouseEvent.CLICK,moveseta);
button2.addEventListener (MouseEvent.CLICK,moveseta);
button3.addEventListener (MouseEvent.CLICK,moveseta);

function moveseta (event:MouseEvent):void{
	Tweener.addTween (seta,{x:*Xvalue of clicked button*,time:1});

but the X valeu should be the buttons X value, so the MC moves to it. How to send this value to the function?