I am starting an online store for custom stationary.

We have built our own custom online engine for users to design their own custom stationary. Each time a piece of stationary is designed with the engine a unique ID number is associated with the design.

I would like to be able to associate an item in someone's shopping cart in Zen Cart with an ID number generated by our custom engine that relates to a specific design.

How can I do this with Zen Cart? Is using attributes the right way to go about this?