Can We Add Fields to a Specific Product

One more question, and I promise I'll leave you alone... well for this week anyways

Is it possible to add a custom field to just one of the product offerings?

Here's the deal... client has members who sign up for an annual fee. I have it set up so that once they've paid for their year's membership, they can then buy an associate membership for a substantial discount. The associate member must reside at the same address as the primary account, so we just need to grab the associate member's name.

Any ideas?

Thanks!