How to Add Coupon to calculated PayPal total?

I would like to offer a discount(promotion) for a limited period by the way of using coupon codes, by the way of having a box just under the total value to pay box, the verifier does not need to see this when they validate the application. Can i do this without changing links as stated above at anytime?

We have a native coupon codes option available for products and subscriptions, but unfortunately, it is not currently available for custom amount fields. I have attached a feature request to this thread, and hope that we will see that option implemented at some point in the future.

Can you please provide us with your requirements about the coupon codes? We can try to check if there are any workarounds.