Open Multiple windows

programming flash
1

Hi
i have a problem with opening multiple windows,

I have a swf file with 5 buttons each button goes to a different url,
so lets say i have 5 buttons, button 1 goes to preloader1 button 2 goes to preloader2 and so on.
the problem is if i click on button 1 and open preloader1, then click on button 2 it opens preloader2 in the same window as preloader1, how would i do it so it opens a different window,
here is the as3 code

 function viewPopup(e:MouseEvent) { 
	
         var address1:String = "room2/preloader.php";
            var jscommand1:String = "window.open('" + address1 + "','PopUpWindow','height=645,width=755,toolbar=no,scrollbars=no,resizable=yes');";
            var url1:URLRequest = new URLRequest("javascript:" + jscommand1 + " void(0);");
            navigateToURL(url1,"_self");
        }
popup_btn.addEventListener(MouseEvent.CLICK, viewPopup);

i have changed this _self to _blank but still doesnt work

any help please