// Enforce only two compare boxes being checked at once.
function enforceOnlyTwoChecked(clickedCheckbox) {
count = 0;
first = null;
form = clickedCheckbox.form;
for (i = 0; i < form.elements.length; i++) {
if (form.elements[i].type == 'checkbox' && form.elements[i].checked) {
if (first == null && form.elements[i] != clickedCheckbox) {
first = form.elements[i];
}
count += 1;
}
}
if (count > 2) {
first.checked = false;
count -= 1;
}
}