I'm trying to set up my Word Press theme to list only specific pages on the nav bar. For my nav bar, I'm using code for a drop down menu that I found on a site. THe nav bar works perfectly. However, how do I set it up to only include the pages I want?

I looked at a site and it said to use

PHP Code:
However, when I use it with my code, it messes up my nav bar. Here's my code. Any idea of what I could try.

PHP Code:
<ul id="nav">  
<?php wp_list_pages('title_li=&depth=1'); ?>
<?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 && is_page()) { ?>  
<ul id="subnav">  
<?php echo $children?>  
<?php } else { ?>  
<?php ?>