I'm freaking out! :-( error #1009 i searched everywhere!

1

TypeError: Error #1009: Cannot access a property or method of a null object reference. at Hospitalroom_fla::MainTimeline/frame1()

i need to assign AS code to a button (“my_btn”). that button is inside 3 other mc’s:

here is it path-

root.mc1.mc2.mc3.my_btn.

i understand i get this error because my_btn is not initialize when i press ctrl+ENTER.

how can i make it initialize anyway?
please please help… i tried everything…

**what can i do? that button must be in that path…
**
the FLA is Attached

and the AS code is:

stop();

buttonMode=true;

mc1.mc2.mc3.my_btn.addEventListener(MouseEvent.CLICK, traceclicked);

function traceclicked(evt:MouseEvent):void {
trace(“my_btn has clicked”);

}

**please please try to help me, i have no idea what shell i do…
**

thank you very much!