post processing – Is it possible in Lightroom to change a develop property of multiple photos by a certain amount?

After a long session of “developing” RAW photos I think I over processed most of the photos. I tried lowering the clarity value of some photos and saw that this tamed the over processed look a bit.

I’m looking for a way to select a set of photos and lower the clarity for all of them by a set amount, regardless of their current value.
I’ve tried Auto-sync, but that sets the clarity of the selected photos to one value.

As an example:
Photo A, B and C have a clarity value of 15, 32 and 12 respectively.
I want to select the three photos and decrease the clarity of all the photos by 10 such that photos A, B and C have a clarity value of 5, 22, and 2.

Is this possible using Lightroom 5?