Add Admin Custom Menu

I have managed to add an custom menu to the admin menu that has a to page called ‘Theme’ and a sub page called ‘Gallery’
Wordpress creates a submenu drop down for the sub pages and calles the first sub menu the same as the group name and the second submenu page ‘Gallery’.

Is there a way of calling the group title one name, the first submenu another name and the second submenu another name.

The best example is if you look at wordpress’s Appearence menu. The group is called ‘Appearance’ and the first submenu page is called ‘Theme’ yet they both point to the same page. This is exactly what I want to do but I cannot find out how to do this using the add_menu_page and add_submenu_page functions.

Any help much appreciated.

Regards