Discount Buy 1 get 1 Free

Hi - My client just asked for a special for Monday!

I am trying to implement; Buy 1 SKU Get 1 different SKU Free in my database driven eCart.

e.g. Buy itemID (SKU) 2072 @ $15.00 get itemID (SKU) 2272 free $0.00

There are 3 product items that I would need to apply this to

I would like to tie this to a merchandising rule for a specific time frame.

I looked at Discounts > Quantity of a specific item in the cart =
I would create a SKU with a price of $0.00 to be added to the cart
maybe I need an if statement

I would rather not use a coupon code if possible, but if it makes it easier I would

I looked at all the post one was close but I don't see how it would work in this application

Thanks in advance!

--------- maybe -------------
I think I have to add the discount - with Presence of an item in the cart tied to the ItemID with an if statement on the cart page such as:
if item 4 add item 15
if item 7 add item 16
if item 9 add item

Please help- Ray Eric anyone... thanks