How to exclude post categories from the main sub menu

Hi there,

I've been working with the BP-Scholar theme, and I've set up a couple of post catgories that I don't want to be included in the drop downs from the main menu.

I'm really happy with how things are looking so far, and this extra change would just be great.

is there some code that I can just tweak? I've already got a new header file in my child folder - so no problem with making the changes there.