Portfolio Sub Categories

I am trying to use your portfolio to show only specific things by using the checkboxes in the portfolio categories.
On the first portfolio page I want it to only show the main categories (Farmer’s Market/Services/Retail Stores/etc)
so if you click on the Services Category then you are shown the subcategories (Computers/Landscaping/Housekeeping/etc)
Then the third tier would be if you clicked on Computers (Web Design/Graphic Design/Repairs)

But the check boxes don’t seem to work this way because on my main portfolio page it shows every category and subcategory and even the third branch.

I have been struggling with this for quite some time and would really appreciate some feedback on how to make this work.

Thanks,

Tara