Allow order only product from one category

Hi,
Is this possible with Zen?

The Basics:

1. Have multiple domains: https://www.newyork.com, https://www.florida.com, https://www.newjersey.com. (all hosted on one server)
2. Each domain has top level categories: Computers, Monitors, Drives, etc.
3. Each category has multiple vendors: StoreA, StoreB, StoreC, etc.
4. Each vendor has multiple products unique to that vendor.
   There is no need for any top level to know about another top level.

The wish list:

1. If select https://www.newyork.com/computers/StoreB, I need the order to be limited to only items from StoreB. I do not want StoreB to need its' own URL.
2. Ideally, when selecting StoreB, have it open in a new window.
3. Customer should be registered on newyork.com and be able to use that registration for any vendor on newyork.com.
4. Processing (payment) should go to a single site that is used for all vendors on any of the sites.

I read about the multisite module, but unless I misunderstood, it is not for this type of situation.

I would appreciate being pointed in the right direction and suggestions.

Thanks,
Jeff

Disregard this post.
I figured out how to do a lot of it.

After re-reading the Multisite module info, I installed it and it works great. So far it seems to do most of what I need.