path = "iface/images/menu/";
  
  function doBtn(btn, state) {
    button = eval ("document.images." + btn);
    if (button) {
      button.src = path + btn + "_" + state + ".gif";
    } else {
      self.status = "wrong button name";
    }
  }
  
  for (var i = 1; i < 5; i++) {
    var img = new Image();
    img.src = path + i + "btn_b.gif";
  }