listing pages

I have a list of 10 pages, lets just say with pages ids 1 to 10.

I list the pages in the side bar using the standard wp_pages syntax

<?php wp_list_pages(‘sort_column=menu_order’); ?>

and I can exclude page lets just say 8

<?php wp_list_pages(‘exclude=8&title_li=<h2>’ . __(‘Pages’) . ‘</h2>’ ); ?>

What I would now somehow like to be able to do is add another list in the side bar which would list just page id 8 and any sub pages it may have.

I dont really want to use the exclude option, say exclude pages 1,2,3,4,5,6,7,9,10 as this will be messy when it comes to maintaining the site.

Any help or ideas greatly appreciated