external swf always opens get url in new window

Hey, I have created an external swf for a presentaion and it will go on a cd. It has a couple of buttons that will open up different web links...
The problem I am having is that each button will open up "its own" browser window...and if you click each button several times it opens several browser windows. (only the first time you use that button though)
I would like the presentation to only open one browser window...no matter how many times you click, or how many buttons you click.
Can this be done?
Thanks for the help!

This is the code I am using for the buttons now:

on (release) {

//Goto Webpage Behavior
getURL("http://www.webaddress.com","_self");
//End Behavior

}