How to save checkbox value without submit?

Question

Drupal

Good day, dear Drupal experts on the 7th. Tell me how to save the value of the checkbox using Drupal (without the submit button)? The code with the checkbox itself:

function checkbox_ajax($form, &$form_state) {
  $element = array(
    '#type' => 'checkboxes',
    '#options' => drupal_map_assoc(array(t('Выполнено'), t('Не выполнено'))),
    '#parents' => array(),
   );
   
   $form_state = array('values' => array());
   $form_Build = form_builder('just_test', $element, $form_state);
   return drupal_render($form_Build);
}