Can you exclude child pages of a specific parent within a navigation?

try -:

if your page ID = 999

<?php
$child_ids = $wpdb->get_col("SELECT ID FROM $wpdb->posts WHERE $wpdb->posts.post_parent = 999  AND $wpdb->posts.post_type="page" AND $wpdb->posts.post_status="publish" ORDER BY $wpdb->posts.ID ASC");
$exclude = implode($child_ids,', ');
wp_list_pages('exclude=" . $exclude . "&title_li=<h2>' . __('Pages') . '</h2>');
?>