AS3 Problem with MC as button

Hello. I am new here.

I have small problem with MC in AS3.

I would like to make a movie clip, that works like that:

When u press it first time, it goes to current frame and play.
When u press it second time, it goes to other frame

I tried to do this that way:

z1.addEventListener(Event.ENTER_FRAME, everyFrame);

z2.addEventListener(MouseEvent.CLICK, nacisk1);

function nacisk1(event:MouseEvent):void {
z2.gotoAndPlay(2);

else

{
gotoAndPlay(20);
}

but it does not work.

z1 is a current MC.

Thanks for help