Stuck in a loop

Hello,
I am a AS 3 newbie…I have a swf within a html page. There is a function that opens an html page when an object gets to a certain x position. However, when the object gets to that point the new html page (in _self) opens over and over again and get stuck in a loop. Any way to escape this loop and what would be the best way to trigger this new html page to open when the x position of the object is true?

Code:
a_mc.addEventListener(Event.ENTER_FRAME, stop_a);
function stop_a(event:Event):void
{
if(a_mc.x<71 && a_mc.x>69)
{
navigateToURL(new URLRequest(“http://test.scheiner.com/advertising.html"),"_self”);
}

Thanks in advance!