Map Macro opposite way

Maybe a stupid question, but I cannot figure it out:

How do I map a macro to work the opposite way. Simple example would be a macro that controls both wet and dry, but one of them in the opposite way, such that when I rotate the macro, the wet goes up, while the dry goes down (to keep the overall level the same).

Thanks in advance.

Nevermind, just figured it out, was too easy

For reference: The solution is to make the min value higher than the max value.