What you say makes sense, instead of having a useCoupon column in the table etc. I'm not sure that I am getting this correct. I added the two recordsets to cart.php
1. rsCandyCoupon from daily_candy table
2. rsCandyOrders from the orders table
3. Session variable usedCoupon
Still allows the coupon to go through even though it is listed in the orders table in couponCode column
Also I notice that sometimes my rsCoupon will change from form variable = txtPromoCode to entered value = a blank. So I have to keep checking it.
Can you take a look at my cart script?