"How did you hear about us?" at checkout

Help! How do I add a box at checkout that I can put "How did you hear about us?" at??

You could try to implement the 'How Did You Hear About Us' contribution from the downloads area: http://www.zen-cart.com/index.php?main_page=product_contrib_info&products_id=186

(I never used it, but it's probably a good starting point)

I've been looking for the general support thread for "How Did You Hear About Us?" add-on. In my search, I've seen a couple of zenners asking about having this at checkout. I'd really like to have it at checkout, too.
It's a perfect setup for something I require except I need information per order, not per customer, since we get a lot of repeat business.
I know my way around html and I can figure out a lot with mysql and php but I was hoping someone could tweak the code just a bit to get me going; or at least offer pointers on adjusting it. I can change everything inside the add-on except tying it to an order instead of a customer. Any help would be greatly appreciated!