use ajax value_form method of views handler

hello iam trying to user ajax callback in my method value_form of my handler and doesnt work, here is my code

 /**
     * Provide a simple select list for equality
     */
    function value_form(&$form, &$form_state) {

        $countries = _prepare_countries_list();
        $selected_country = isset($form_state['values']['value']['country'])?$form_state['values']['value']['country']:key($countries);
        $values = array(
            'country' => array(
                '#type'    => 'select',
                '#title'   => t('Country'),
                '#options' =>$countries,
                '#ajax'    => array(
                    'callback' => 'country_state_dependent_dropdown_callback',
                    'wrapper'  => 'dropdown-states',
                ),
            ),
            'state' => array(
                '#type'    => 'select',
                '#title'   => t('State'),
                /*'#options' =>array(
                    'All'       => t('--Any--'),
                    'tunis'     => t('Tunis'),
                    'marseille' => t('Marseille'),
                ),*/
                '#prefix' => '<div id="dropdown-states">',
                '#suffix' => '</div>',
                '#options' => _country_state_get_second_dropdown_options('france'),
            ),
        );
        $form['value'] = $values;
        return $form;
    }

   function country_state_dependent_dropdown_callback(&$form, &$form_state) {

       return $form['value']['state'];
   }

any solution to fix that problem