Help gotoAndPlay("Scene",1) invalid coercion ..

i just made a simple flash ..there's 2 scene : "Scene 1", and "Collections"

and then i added a button .. "btn_coll"

then i wrote this in the actionscript

stop();

btn_coll.addEventListener(MouseEvent.CLICK,tombol);
function tombol(event:MouseEvent):void{
gotoAndPlay("Collections",1);

}

and when i play it, it said Invalid Coercion of a value of a Int to a undefined string.

why it's error?

thanks.. please help ASAP..