Show categories to assigned user groups

I have several categories in Hikashop, that may only be shown to assigned users.
The user must give a specific code to be assigned to his group. After succesfull assignment, the user can see the products in his group and insert products in his cart. I the checkout flow he must give his Name, Address, Email ect. to end his order.

To give an example:
2 categories HKS1 & HKS2 are not visible for public users.
User1 knows the code to make category HKS1 visible for him. He fills in a form with that code.(1?)
After browsing he has inserted two products in his shopping cat. To order these 2, he must register as a customer in hikahop to succesfully complete the order procedure.

How can I set up this with Hikashop?
How to create the form as shown @ (1?)