How to solved limited discount

V5 Question
#1

We have promotion with bank, when used credit card get discount 10%, with limit transaction not more Rp 2.000.000,-.
If total transaction more than 2.000.000, such as
Subtotal transaction. 3.000.000
Discount 10% 200.000
Total after discount 2.800.000

How make this discount?

#2

Can probably use a payment processor for that which uses a calculation for the 10%.

#3

This promotion just for 3 type credit card, others not get discount 10%. And this promotion just for 1 month.
I use payment description option button for type of credit card