Go to url

I need help badly. I’m trying to set up a button in flash mx2004 that goes to a url. I keep getting an error that says “statement must appear withing on handler”. When I do a “test movie” it seems to go to a file and not to the url. After clicking on OK the blank browser opens. The Code I’m using is:

this.url_btn.onRelease = function () {
} ;

I appreciate any help.