function uncheck_individual_options(cbox) {
    if (cbox.checked) {
      var boxes = cbox.form[cbox.name];
      for (var i = 0; i < boxes.length; i++) {
        if (boxes[i] != cbox) boxes[i].checked = false;
      }
    }
  }
  function uncheck_ALL_option(cbox) {
    if (cbox.checked) {
      var boxes = cbox.form[cbox.name];
      for (var i = 0; i < boxes.length; i++) {
        if (boxes[i].value == "") boxes[i].checked = false;
        break;  // only one ALL option per checkbox group
      }
    }
  }