function disable_me(){
  if (document.select_form.select_D.options[document.select_form.select_D.selectedIndex].value == "D1") {
    document.select_form.select_E.options[0].selected=true;
    document.select_form.select_E.disabled=true;
    document.select_form.select_E.style.color="#bbb";
  }
  if (document.select_form.select_D.options[document.select_form.select_D.selectedIndex].value == "D2") {
    document.select_form.select_E.disabled=false;
    document.select_form.select_E.style.color="#000";
  }
}