var message="Desabilitado"; 

function init(){
	try{
		topoSWF_DoFSCommand("dthr", "");
	}
	catch(e){}
}

function click(e) {
  if (document.all) {
    if (event.button == 2) {
      alert(message);
      return false;
    }
  }

  if (document.layers) {
    if (e.which == 3) {
      alert(message);
      return false;
    }
  }
}

if (document.layers) {
  document.captureEvents(Event.MOUSEDOWN);
}

<!-- document.onmousedown=click;