AbleCommerce Shopping Cart Software

Quick question: I have several items that are only available in multiples of 3/6/12 etc. However, they are listed as singles for pricing in our db. I am trying to figure out a way to make sure these items are only ordered in multiples of 3/6/12 etc. I have the min qty set correctly and that works fine. But for the life of me I am not seeing a way to get additional increases to the order count to remain in multiples. Any ideas? Or maybe I am looking at this all wrong?

Take a look at our site:
http://www.poolgeek.com/BioGuard-Silk-Sticks-P1117.aspx (for example)
We use kits to accomplish what you are (I think) looking to do.
We create a fake product (with price zero) that contains kit components which consist of multiple kit products. That way, one product can contain all the relevant sizes and case quantities for any specific product type.
Is that kind of what you are looking for?

Scott