Add new trigger on Code validation

Once a user has correctly entered the confirmation code to activate their mobile phone number, it would be nice to have them automatically added to a certain role. It could be done quite easily by adding some code after user_save in sms_user_settings_confirm_form_submit. In fact the following code achieves this, but is hard coded to a single role which is in use on one of my websites:

     $rid = 6;
     $role_name = db_result(db_query('SELECT name FROM {role} WHERE rid = %d', $rid));
     if ($account !== FALSE && !isset($account->roles[$rid])) {
         $roles = $account->roles + array($rid => $role_name);
         user_save($account, array('roles' => $roles));
     }