Category and child categories

After searching for ages I beginning to pull my hair out on this! I had some code working for pages where the child pages would be listed if there were any. It looked like this:


<div id="sidebar">
<?php if(wp_list_pages("child_of=".$post->ID."&echo=0")) { ?>
<span class="navtitle"><?php bloginfo('description'); ?> Categories</span>
<ul class="subnav">
<?php wp_list_pages("title_li=&child_of=".$post->ID."&sort_column=menu_order&show_date=modified&date_format=$date_format&depth=1");?>

<?php } else { ?>
No Page
<?php } ?>


For a few reasons i’m trying to do exactly this for post categories, so if i’m on a post within a certain category it would show the child categories in the sidebar.

Is this possible?

Thanks for any help.