Display a different (custom) menu on a page?

We recently (this week) migrated our Thesis theme to GP Premium. The only thing I can't figure out is how to load a different menu on different pages.

We have our public site. Then we also have a customer Academy area (backend membership) that houses all our paid products.

site.com right now loads the default/primary menu.

We now need site.com/academy/ to load our Academy menu.

And then yet a different menu based on a course, like this:

site.com/academy/product-1/
site.com/academy/product-2/

With Thesis we could simply call any WP Menu from any page (via a drop down). Nice and easy.

Any help would be hugely appreciated, Tom.

Thanks!

André