How do I require a product must be purchased?

Hi all,
this is a new installation and my question is a theoretical one about setting up products.

The customer that will be using Zen Cart is a club. They want both guests and registered members to be able to view the products for sale, however in order to purchase a product you must first be a member, like with Costco.

In addition to all the products listed for sale there are a couple of membership types, 1 year, 2 year, etc.

My question is, if a guest attempts to purchase a product how do you block the purchase until they purchase one of the above memberships? Is this possible through the product attribute function?

Many thanks in advance.

Regards,
Henry

You could try the One-Time Membership Charge module. It adds a one-time charge to your shopping cart when you set up an account. However, it was written for 1.3.7. It's also limited to a single fee structure. You'll need to hire a developer to modify the file to make compatible for 1.3.9 or 1.5.

Thanks for the reply.

Neglected to mention that an ERP system "feeds" guests and members into Zen Cart, in other words the individual is passed to Zen Cart from the other system (as a registered user) and they may or may not be a member of the organization. Therefore I was looking for a solution that was more product-centric as a person's membership could expire each year.