Using relative/dynamic values in conditional formatting of data colours in shape map

Hello,

Is there any way to add relative values in the data colours parameters, rather than just absolute values?

When I add filters to reduce the sampled data, the absolute middle value I use is no longer an appropriate value to use to provide a useful range of colours to spot differentiation between regions.

Is there a way to use a median as the middle value, so that the colour dynamically changes to different filters used?

Thanks!