Buttons in ActionScript 3.0

Hello,
I'm trying to make my buttons clickable in flash CS4 ActionScript 3.0, but for some reason it keeps giving me the error - 1120: Access of undefined property btnHome. I have set it ups as - Instance of: btnHome and name home. What am I doing wrong? Please help!

My code looks like this

function goHome(event:MouseEvent):void
{var targetURL:URLRequest = new
URLRequest("http://www.spintopdesigns.com/");
navigateToURL(targetURL);}
btnHome.addEventListener(MouseEvent.CLICK,goHome);