Listing subpages

how do i list the subpages in the parent page itself? I would like the parent page to be somewhat of a ‘table of contents’ the contents being the subpages.

also, how can i alter the following `
<?php
$thispage = $wp_query->post;
if($thispage->post_parent!=0)
{
wp_list_pages(“title_li=&child_of=”.$thispage->post_parent);
}
else
{
wp_list_pages(“title_li=&child_of=”.$thispage->ID);
}
?>
`
so that when i click A i get A1 and then when i click A1 i get A1a

[no page selected]
A
B
C
D

to

A[page A is selected]
-A1
B
C
D

to

A
-A1[page A1 is selected]
–A1a
B
C
D

etc..?