Listing page with all its children in a list

Hi,

I have this page: https://icomprintmanagement.co.uk.s88828.gridserver.com/healthcare/

What i’m trying to do is have the 12 categories in the panel at the bottom to pull out the lists below them using wp_list_pages

I have this code

if($post->post_parent)
  $children = wp_list_pages("title_li=&child_of=".$post->post_parent."&echo=0");
  else
  $children = wp_list_pages("title_li=&child_of=".$post->ID."&echo=0");
  if ($children) { ?>

<ul>
  <?php echo $children; ?>
  </ul>
  <?php } ?>

But Want I want to do is tell the function to pull the children of a certain page… not the page it’s actually on..

So for example I have 12 pages which all have their own child pages on the web page mentioned above, I’d like each one of the 12 pages to pull it’s children into a list..

How do I do this? Any help would be great