function setCheckForm(myForm) {
   for (i = 0; i < myForm.elements.length; i++) {
      if (myForm.elements[i].type == 'checkbox') {
           if (myForm.elements[i].checked == false) {
               myForm.elements[i].checked = true;
               myForm.elements[i].value = "f";
            } else {
               myForm.elements[i].value = "t";
            }
        }
    }
}