var newWindow;
	function openPopup(popup_width,popup_height,popup_url,var_name){
			var windowHeight = popup_height;
			var windowWidth = popup_width;
			var windowName = var_name;
			var windowUri = popup_url;

			var centerWidth = (window.screen.width - windowWidth) / 2;
			var centerHeight = (window.screen.height - windowHeight) / 2;

			if ( !newWindow || newWindow.closed ){
				newWindow = window.open(windowUri, windowName,'addressbar=0,menubar=0,location=0,status=0,scrollbars=yes,resizable=0,width=' + windowWidth + 
					',height=' + windowHeight + 
					',left=' + centerWidth + 
					',top=' + centerHeight);
			
			}
			 if ( newWindow && ! newWindow.closed ){
				newWindow.location.replace(windowUri);
				newWindow.focus();
			}
	}