How to Link main stage from inside of a movieclip?

programming flash
1

I created “symbol1” movie clip. And I have dynamic text “myscore” on the main stage.

I have this code inside of “symbol1”.
[COLOR=Blue]
mybutton.addEventListener(MouseEvent.CLICK, b1);
function b1(event:MouseEvent):void {
myscore.text = “30”;
}[/COLOR]

And it gives me this error.
[COLOR=Red](1120: Access of undefined property myscore.)[/COLOR]

It works only when text and actionscript inside of the same symbol. I tried like this [COLOR=Blue]root.myscore.text = “30”;[/COLOR] but it still doesn’t work.