function reservation_dialog( id )
  {
    url = '/php/reservation.php?customer_id=' + id;
    win = new Window('window_id', {className: "dialog", title: "Tisch-Reservierung", width:500, height:300, url:url, minimizable:false, maximizable:false });
    win.setDestroyOnClose();
    win.showCenter(true);
  }