customize page subnavigation.

I’m trying to come with the simple code to place in my sidebar.php, to tell wordpress to:

If page is “X” than display the subnavigation header “custum nav title”
Else, do your normal routine.

should be a simple PHP command but i know almost zero PHP… please help?

i’m including the code from sidebar.php to point out where it’d need to go

<?php /* Menu for subpages of current page */
                        global $notfound;
                        if (is_page() and ($notfound != '1')) {
                            $current_page = $post->ID;
                            while($current_page) {
                                $page_query = $wpdb->get_row("SELECT ID, post_title, post_status, post_parent FROM $wpdb->posts WHERE ID = '$current_page'");
                                $current_page = $page_query->post_parent;
                            }
                            $parent_id = $page_query->ID;
                            $parent_title = $page_query->post_title;

                            if ($wpdb->get_results("SELECT * FROM $wpdb->posts WHERE post_parent = '$parent_id' AND post_type != 'attachment'")) {
                        ?>
                    <li class="widget">
                       <h2><?php echo $parent_title; ?> <?php _e('Options'); ?></h2>
                      <ul class="list-page">
                        <?php wp_list_pages('sort_column=menu_order&title_li=&child_of='. $parent_id); ?>
                      </ul>
                    </li>
                    <?php } } ?>