Wordpress menu displays all child page link but also want to filter to be based on custom field

Hi I've got this menu that display all the child page menu of the current page works fine to that point, but i now only want to display the child pages that custom field has value of (thememenu) but it still diaply all the child page when I try help please

<ul>
<?php // display all the child and granchild page links exclude link of page parent_pages_to_exclude

$extra_menu = get_post_meta($post->ID, 'extra_menu', true);
$parent_pages_to_exclude = array(198,701,3247); // excluded pages
foreach($parent_pages_to_exclude as $value) { // for each value inside array parent_pages_to_exclude add the value in the variable value
if ($page_exclusions) { $page_exclusions .= ',' . $value && $extra_menu == "thememenu"; } // this has the values of all the child pages excluded and included
else { $page_exclusions = $value; }
}
wp_list_pages( array('title_li'=>'','depth'=>3, 'exclude'=>$page_exclusions,'child_of'=>get_post_top_ancestor_id()) );

?>
</ul>

 

Question: why don't you use the built in wp menu system? (ie, from the admin panel)