Does an Addon exist for customizing customer discounts?

I recently installed v1.5.5a on a customer's site - this was all new, no previous site or zc version had been installed - and everything is working as it should. I also installed EZ Poplulate 4 and uploaded about 1100 products from his Quickbooks files. All seems to work ok, as well.

However, now my customer tells me that he does discounts for his customers (he has about 100 customers - none of which have been added to the shopping cart yet), and while I told him ZC can do discounts, what he's telling me he gives different discounts on different products to different customers. In other words, Customer Mike might get a 5% discount on product-A and a 10% discount on product-B and $10 off on product-C, while Customer Bob gets a 2% discount on product-A, no discount on product-B, and a 15% discount on product-C. In other words, EACH customer pays something different on MOST of his products and there is no "across the board" discount on any given product to every customer. It is all very random. Quickbooks allows him to do this. Is there any kind of add on available out there to integrate into ZC to allow him to do the same?

You might check whether there's something suitable here: http://www.thatsoftwareguy.com/zencart.html