I am making a holiday notification to display on the header,

1. INSERT INTO configuration (configuration_id, configuration_title, configuration_key, configuration_value, configuration_description, configuration_group_id, sort_order, last_modified, date_added, use_function, set_function) VALUES (NULL, 'Enable Holiday Notification?', 'Holiday_Notification', 'Disable', 'Do you want to enable Holiday Notification?', 20, 21, now(), now(), NULL, 'zen_cfg_select_option(array(''Enable'', ''Disable''),'),
(NULL, 'Holiday Notice Content', 'Holiday_Notice_Content', 'Notice:We are taking holiday', 'Enter your Holiday Notice Content', 20, 22, now(), now(), NULL, NULL);
(in Website Maintenance group)

2. add code on includes/init_includes/init_header.php :
if (Holiday_Notification == 'Enable'){
$messageStack->add('header', HOLIDAY_NOTICE_CONTENT,'caution');
}


I expect it to work like WARN_BEFORE_DOWN_FOR_MAINTENANCE but it doesn't, can somebody help me on this issue, which file(s) I still need to modify?