Voucher and category

[krupers]

I have a question about vouchers on Prestashop.

Now I am set up with:
- voucher
- rules
- categories
- validity

But.... I have products from a "Category1" and products from "Category2". I can set that to let user a chance to apply a voucher there have to be a rule of "at least" one product from selected category (Category1"). If user add another product to basket - from Category2, this product also takes a voucher discount. I want to be sure, that discount is limited only for a products from Category1 - no excludes.

So now if in basket we have:
- productCat1 = 100 USD
- voucher for Cat1 = 50%
TOTAL: 50 USD <- THAT IS OKAY!

If in basket we have:
- productCat1 = 100 USD
- productCat2 = 100USD
- voucher for Cat1 = 50%
TOTAL: 50USD+50USD = 100USD <- THAT IS *NOT* OKAY!!!!! (should be 50+100 = 150 USD).

Okay, I know that I can exclude separate products that are not affected with coupon, but what are categories for then?
If I want to add a coupon for a single category only, products that are not from that category should not be affected with coupon, am I right?

What should I do to apply coupons with.... "logical expression" I am thinking, but Presta has "logic" declared by itself :D