I have a scenario as follows:

Product A from Category 1 and Product B from Category 2.

If a customer buys 1 qty of each product, then he/she will get a 10% discount on the cheapest product. This scenario works fine if the customer buys these two products only in that order.

If he/she purchases another product which is not included in the promotion and less than the price of the above two in the same order, then the discount applies to the third product (because of the cheapest price).
How can I handle this situation?