69123 SunShop: Buy 2, Get 1 Free Mod

Before you bid, this website is going online later this week, and I would like to have this module completed within 3 or 4 days of that time... don't bid on this if it's going to take longer than 3 or 4 days for you to complete. This sunshop modification for a new website, therefore you aren't working on a live server with customers placing orders. Buy Two, Get One Free Module: When a customer purchases any two specific items from certain categories, they will be given the option to choose a free gift. The choice free gifts should be presented to the customer during the checkout process, and should be added to the customers shopping cart and invoice, but market as free. The selection of categories for which products will apply should be variable, and the selection of what 'free gifts' are available should be a variable. For example, if a customer purchases anything from Category 1, Category 2, Category 5 or Category 8 they will be able to choose Free Gift Item # 2, Free Gift Item #5, Free Gift Item #7 or Free Gift Item #11. The categories will remain constant, but new categories may be added in the future. The free gift items may change weekly. It would be nice to have a "Free Gift" category, and whatever items are 'active' are the items customers can choose from. Each week I can change the free gift option depending on current inventory. PLEASE let me know if you have ANY questions... Thanks!