How do disable coupons for products when dynamic pricing kicks in?

Hi there.

I have a deal running on my website at the moment using dynamic pricing (2 for $xx, 3 for $xx). How can I disable the use of coupons when dynamic pricing is in effect?

I don’t want to restrict the product under the coupon itself because if someone is only purchasing one of the item then the coupon would be valid (i.e. 10% off).

However if someone is already getting a discount with 2 for $xx then I don’t want them to be able to apply the 10% off coupon to receive a further discount.

Thanks in advance.