Search Multicategory

I search for a solution for:

search sub category in two different main categorys.

eg.

Category 1

SubCategory 1

SubCategory 2

Category 2

SubCategory 1

SubCategory 2

There should be possibility to for eg. show all post from Cat 1 / SubCategory 1 and Cat 2 / SubCategory

Is there anybody that know how to do this, or if there is any plugin for it, have search but dident found anything

Thanks