Category Dropdown menu

I’m using wpsc_start_category_query to list a menu from the category list. I use the child of option and this makes a great nag menu. I need to add drop down menus to some and want to have wordpress automatically add a drop down if a child category is created. Anyone have any idea how or where I should look to create this?

http://s501063316.onlinehome.us

Thanks

http://wordpress.org/plugins/wp-e-commerce/