function check_all(form) {
  for (i=0 ; i<form.elements.length; i++) {
    if (form.elements[i].name == "pctvcheck") {
      form.elements[i].checked = true;
    }
  }
}
function uncheck_all(form) {
  for (i=0 ; i<form.elements.length; i++) {
    if (form.elements[i].name == "pctvcheck") {
      form.elements[i].checked = false;
    }
  }
}