Map Chart diverging by Column, variable or calculated value

Lass

Use case: Build a map where the provinces are red whenever their performance in percentage is lower than the country average performance and green otherwise. Right now this is impossible.

At the moment the ability to set a green or red visual clue is determined by either The mean, the median, zero or a fix number set un 'Manual'.

The problem is that whenever we are dealing with percentages or any kind of fraction the mean of the country is diferent that the mean of the values due to algebra.

I'd love to be able to reference a field, a formulae or something that gives me the option to customize the zero of the diverging color map.