Can I exclude a page from the navigation?

Hi
I am using this code in the the header:

<?php 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 id="subnav">
	<?php echo $children; ?>

Is there any way to tweak it to exclude certain pages? For example, can I add a minus sign somewhere and the ID of the page?

thanks