var popwin="";

function popwindow(file, target, width, height) 
{
  	if(popwin && !popwin.closed) popwin.close();
 	popwin=window.open(file, target ,"toolbar=no,location=no,directories=yes,status=yes,menubar=yes,scrollbars=yes,resizable=yes,width="+width+",height="+height);
 	popwin.focus();
  
};