Limit Gift Certificate Use To Products

Has anyone done any work to limit a GC usage to a set of products? I.e. instead of giving the list of products for free, to have that list (or a list from the get_gift_certificate_info hook) be a list of eligible products where the GC's usage is limited to that set and the GC amount is adjusted based on the price of the eligible products in the cart?

I.e. GC amount of $10.

Free products (or other list of products) has:

abc - ($2)

def - ($5)

hij - ($7)

Cart contains:

1 -xyz (not in GC list, rice = $5)

2 - abc

Non-GC total would be: 5 + 4 = $9

After application of GC (only 'abc' is eligable for usage): $5

GC Balance is $6

Before I go do this work, thought I'd check to see if anyone's already done it an wants to sell the code. Seems this would be great added functionality to the GC addon in cs-cart.

i want to offer Free Products at the checkout of total Order amount. i want that each customer choose a one free item at the checkout
One Order 1 product for free
i will offer many types of product for Free with each order total but i want that customer have ability to choose only 1 item per Order.
kindly let me know if someone can help me how to do that.