One code for One coupon -
 To simply make a coupon only applicable to specific products, then enter a unique coupon code for the products that the coupon is applicable to in the "add product" or "edit product" screen. The code must be alphanumeric and start with a letter.
 I.E. - E23, OIL, COUPON1 would all be legitimate codes. (the code can use capital or lowercase letters, but you must use the same case for both the code and the restriction)

 Then for the coupon itself, enter the code that the coupon applies to in the Restrictions field. For instance, if the coupon is vaild for oils only, then you could use a coupon code of "OIL" for each of the oils that the coupon is valid for, and put "OIL" in the coupon Restrictions field. If the coupon is used and no products purchased have the "OIL" coupon code in them, the customer will get a message that the coupon is not valid for that order.

Multiple Codes for one coupon -
 If you want to make the coupon valid for products with different codes, then you can create a logical statement as to what is valid as well.
 I.E. Lets say that you have grocery items, and the coupons are valid for peanuts and for butter, and the peanuts have a code of "NUT" and the butter has the code of "BUTTER". Then the coupon will be valid if the Restrictions field is filled in with "NUT ^ BUTTER". The "^" denotes an "or". Or if the coupon is valid only if they purchase both peanuts AND butter, then use the logic of "NUT & BUTTER". In this case the "&" means "and". The logical statement can also contain parenthesis "(" and ")" like "(NUT & BUTTER) ^ PEANUTBUTTER" would be either "peanuts and butter", or peanut butter assuming that peanut butter had the coupon code of "PEANUTBUTTER".

Note that for efficient processing of coupons by the cart, all terms are expanded out to goupings of ands ored together with no parenthesis. What is entered and what is stored will be boolean equivalents.

Quantity Limits for Products -
 You can also apply a minimum quantity for each product. Lets say that you have butter in 1 pound and 5 pound containers. The coupon is for a purchase of 3 or more pounds. If the coupon code for this coupon is "BUTTER", then you can use "BUTTER" for the coupon code for the 1 pound container, and "5BUTTER" for the 5 pound butter. Then for the coupon itself use the restriction of "3BUTTER". The cart will add up all the BUTTER codes and check that they equal or exceed the "quantity" of "BUTTER" codes specified in the restrictions. If the coupon had "7BUTTER", then either 2 one pound and a 5 pound must be purchased, or two 5 pounds. Of course the number preceeding does not have to pertain to weight, it is simply a way of assigning different values for different items if you need more than 1 of that value for the coupon to be valid. Since a number in front of the coupon signifies a quantity, codes cannot start with a number.

Negative Code Comparisons -
 Negative comparisons can be made as well. For instance, if you are wanting a coupon to apply to everything but gift certificates, and the gift certificate has a code of "gift", then if the coupon has a restriction of "!gift", all items except the gift certificate will apply. This can be entered into a boolean equation just like any other term with the exception that quantities are not supported. That is, "!3gift" is not valid, quantities are not checked on negative comparisons.