Sub Child Pages – Jump Menus

Hi guys.. i’m wondering if anyone could point me in the right direction.

I’m trying to create a menu system as such..

<menu>
<parent>Parent Page</parent>
<title>Subpage</title>
<jump_menu>Subpage children</jump_menu>

<title>Subpage</title>
<jump_menu>Subpage children</jump_menu>

<title>Subpage</title>
<jump_menu>Subpage children</jump_menu>
</menu>

While I can get the subpages to display with their children using this lovely peice of code..

<form action="<?php bloginfo('url'); ?>/" method="get">
					<?php
					if($post->post_parent)
					$select = wp_dropdown_pages("sort_column=menu_order&selected=".$post->ID."&title_li=&child_of=".$post->post_parent."&echo=0");
					else
					$select = wp_dropdown_pages("title_li=&child_of=".$post->ID."&echo=0");
					$select = preg_replace("#<select([^>]*)>#", "<select$1 onchange='return this.form.submit()'>", $select);
					echo $select;
					?>
					</form>

I can’t seem to seperate out the child pages of the subpages..

I thought about creating two arrays but these seems overly complicated..

Anyone else done something similar on a theme or project that could point me in the correct direction.