purchase access to directory via Zen Cart

I have had Zen Cart (v1.3.9h) installed and functioning on my website for some time now. I understand how to make certain files downloadable when purchased by registered users. However, I would like for my Zen Cart's registered users to be able to purchase access to a whole directory on my website (accessible via that specific user's login and password info). For instance: - the user purchases access to a particular directory - the user goes to that directory, say, "/gen", on my website - the user is prompted for a login and password - the user gives his/her login and password, and if s/he has in fact paid for access to that dir, is able to access pages in the directory The purpose of this is so that the user can purchase access to use various javascript calculators in the directory. (NOT download them; just use them live.) (Eventually I can imagine wanting to make multiple directories separately purchasable.) As I don't know if this is directly doable using Zen Cart and generated permissions or would require something else, I am not sure what to make the price for this project. Thanks.