var meinfenster = false;

function popup(link, name, breite, hoehe) {
  meinfenster = window.open(link, name, "width="+breite+",height="+hoehe);
  meinfenster.focus();
}

function CloseMyWindow() {
  if(meinfenster) {
    if(!meinfenster.closed)
       meinfenster.close();
   }
}