list all post of a category as dropdown of a category in menu

hello
i have created a menu using css and wordpress function .and its working fine.but i need to list down the post under a category as the second tier in the menu.
Suppose i have 2 category and 4 post like this
-category1
–post1
–post2
category2
–post3
–post4
Now I need to show the post in dropdown under the catgory.
I have tried this code but its not working
<ul id=”nav2″ class=”clearfloat”>

• /” class=”on”>Home

<?php wp_list_categories(‘orderby=name&exlude=181&title_li=’);
$this_category = get_category($cat);
if (get_category_children($this_category->cat_ID) != “”) {
echo ”

“;
wp_list_categories(‘orderby=id&show_count=0&title_li=&use_desc_for_title=1&child_of=’.$this_category->cat_ID);
echo “

“;
}

?>

Thanks in advance