We have an e-commerce form to which we would like to add a coupon/discount code like any shopping cart.  We will need to be able to add/remove coupons based on the date/time or number of entries submitted.  The discount would need to stay (and be edited) while the form is being processed by the editor/admin.  This form is a bit different than standard shopping carts as the entries submitted by the users are updated periodically, pricing changes... ie from the estimate (initial entry) to completion, and the final bill is sent.
We would like the coupon to look like:
'March Madness '  and the user would get a 10% discount.
 
Coupons will not apply to the shipping and insurance estimate of the form.