Ability to exclude listing from main category

I was wondering if it’s possible to exclude a listing from a main category when it’s posted in a subcategory.

In other words, if I have a category ‘Professionals’ and subcategories ‘Architects’, ‘Quantity Surveyors’ etc., and I submit a listing under ‘Architects’ without explicitly selecting the main category ‘Professionals’, then the listing should not be visible if I simply search ‘Professionals’. I would have to search the subcategory ‘Architects’ to see the listing.

The reason for this is that we would like to charge a fee for the privilege of advertising directly under main categories using the ‘Extra Price Per Category’ feature.

Another question I have that goes hand in hand with this is how to display a category’s subcategories somewhere (preferably at the top of the page) when I search the main category.

Any idea whether this is possible, and how?