Restrict access to my store

Hi...
I'm using my store in conjunction with an affiliate program to allow Sales Reps to place orders for their customers. Each Sales Rep/Affiliate has a unique link on their browser which takes them to the Registration page of my Zen Cart, and in doing so, records data in the affiliate program to track the Sales Reps performance etc.
The Sales Rep then places an order using their customers data, in the usual way.
Because of our contractual arrangement with the Sales Reps, we cannot allow customers to independently order from the Zen Cart by registering themselves.
I'm trying to figure out how to restrict access to the store to only the Sales Reps who access the Registration page through their 'affiliate' link.
I've been tinkering with adding an additional Login field to the registration page - but would rather not add another level of complication.
Any suggestions?
Thanks

There are various levels of "viewer permissions", some of them set in CONFIGURATION>>>CUSTOMER DETAILS>>>CUSTOMER SHOP STATUS - VIEW SHOP AND PRICES (Option 1 is probably for you).

Then, you will Authorise your customers (sales reps) manually - so if a stranger tries to register, you just deny them access by not manually approving their registration.

Other settings include: CONFIGURATION>>>MY STORE>>>STORE STATUS