function popup(mylink, width, height)
{
  try { 
    if(!popupwin.closed) { 
      throw "Error 1"; }
		 else
		 { throw "no error"; }
    } 
  catch(er) {
    if(er == "Error 1") 
      popupwin.close();
      popupwin = window.open(mylink, 'popup','width='+width+',height='+height+',scrollbars=yes');
      return false;
 	  if(er == "no error")
      popupwin = window.open(mylink, 'popup','width='+width+',height='+height+',scrollbars=yes');
      return false;
  } 
}