Creating hidden variables, setting quota counts and limits....

I have some questions about creating hidden variables, setting up quotas to ensure I don't collect more than I need, and also to ensure ratio of Group A, B is even when I randomly assign them to rate one of the product concepts.
Let’s say there are two subgroups I want to create; I also want to set up a quota on each of those subgroup on the backend. Lastly, I want to test 4 product concepts, but will randomly assign 1 of the 4 to each individual.
For example,
Q1. How often do you visit Store X?
-       Once a week (Group A)
-       Twice a week (Group A)
-       Three times a week (Group B)
-       Four times a week (Group B)
-       Five times a week (Group B)
Part 1. Depending on what they choose, I want to put people into Group A or Group B. I want to create a hidden variable, Q2, with 1=Group A, 2=Group B.
Part 2. I want to set a number limit on Group A (n=400), and Group B (n=400).
Part 3. The last piece is… I want to randomly assign one of the four product concepts, so each person only sees one concept. When I do this, how can I balance Group A/Group B quota for each concept?