Help Tweening Rotation 180 degrees on each button click

[Crash886]

Hi ! I have what is hopefully a quick question. I have set up a motion tween using the flash tween class to rotate an image 180 degrees. However, if I should want to work wit hthe image from that point (say click the button again and have it rotate another 180 degrees back to its original position) I can't. It will simply run the tween again because my function specifies to go from 0 to 180. Does anyone have any idea how I can use the tween class to rotate this image 180 degrees on each button click? Thanks in advance for your input. Code is below.

import fl.transitions.*;
import fl.transitions.easing.*;
import fl.transitions.Tween;

rotation1_btn.addEventListener(MouseEvent.CLICK, rotateThePicture);

function rotateThePicture(event:MouseEvent) {
//IMG11_mc.rotation += 180;
var PicRotation:Tween= new Tween(IMG11_mc, "rotation", Strong.easeInOut, 0, 180, 5, true);
};