Position of submenu pages in admin menu

Is there a way of setting the position of pages created using the add_submenu_page function in the admin area? I know you can set the position of top level menus created using the add_menu_page function, but I can’t find any mention of how to position submenu pages.

Basically, I’ve created a top level menu called ‘Sermons’. I’ve registered 4 custom post types (Messages, Series, Meetings, Speakers) which have been set to sit inside this menu (using the ‘show_in_menu’ argument).

The problem is, I’ve also created a submenu page called ‘Add New’ (using the add_submenu_page function) which I want to be the first submenu link under the ‘Sermons’ menu. By default it sits at the bottom of the submenu (underneath the custom post type links) and I can’t find any way to move it to the top.

This is how the admin menu currently looks:

– Sermons
— Messages
— Series
— Meetings
— Speakers
— Add New

I want ‘Add New’ to be the first sublink, not at the bottom.