var WindowObjectReference = null; // global variable

	function popup(strUrl, strWindowName,h,w)
 {
  if(WindowObjectReference == null || WindowObjectReference.closed)
  {
  	if (h==null) h = 410;
  	if (w==null) w = 330;
    WindowObjectReference = window.open(strUrl, strWindowName,
           "resizable=no,scrollbars=no,status=no,height="+h+",width="+w);
  }
  else
  {
    WindowObjectReference.focus();
  };
 }