I'm wondering if anyone has an excel formula or the knowledge to create one for the following.

On our drawing register there are fixed reference columns giving the sheet size and current revision (Letter), I am trying to get this value to automatically update as the revision changes overtime, due to most people in the office my self included often forget to up date the reference column.

Rev Size
C A1 A B C

There would naturally be blank spaces where a drawing hasn't been revised but others have been.

I've posted this in the hope that someone has already found a solution, having searched extensively on the net and not found a solution that works.