Group Discount for different categories, Quantity Discount on other categories

I am new to the Zen Cart environment; I am using Zen Cart 1.3.8a
I added the quantity discount addon. The quantity discount is working correctly.
I have search through the forum, but did not find what I am trying to do.
I have multiple categories, one being closeouts. The closeout category is what I have set for quantity discounts. I need to be able to apply multiple group discounts to a category, but only items in that category. Currently the group discount applies to all items in the cart, including the already discounted closeout items.
Is there anyway to change this to only apply to the items within a category?

Yes. The Quantity Discount contribution has user exits which allow you to limit its application to only specific categories (or products). Read the documentation about apply_special_category_discount().

http://www.thatsoftwareguy.com/zencart_quantity_discounts.html

You can also get to this link by pressing the help link in Admin when you're looking at Quantity Discounts under Admin->Modules->Order Totals.

Yes, the quantity discount is working correctly for just the closeouts category. I need to now have multiple group discounts that will apply to only certain other categories. Currently if I try to apply a group discount of 10% it is applied to everything in the cart, which could include items from the closeout, already discounted items.

You have to write software to do this; there's nothing built in.

Thanks for the reply. Any ideas on what kind of effort it would take to put something together for this type fo group discounting?