Excel If cell is blank sum number of blank cells for a total

I am trying to work on a formula that will help me keep track of which rev items that are still labeled open. The picture below shows what I mean.

I need a formula that checks if the Action Date Closed is blank and total the amount of open Revs for that specific Rev number. In the example below there is one RR2 not closed and one RR1 not closed. I am trying to keep track of all open revs, in a pie chart and need this total column on the top to reflect a summary of the table below.

Any help is greatly appreciated thank you!