How to automate monthly metric?


My customer is looking for a month over month metric for a dashboard

Essentially, how many rows out of the total have a check mark in a certain column at the start of each month.

They want to be able to see the trends over time, so I need to show all the months as time passes.

Counting the check marks with a =COUNT formula in a sheet summary is easy to set up but I cannot figure out how to automatically capture the count each month without over-writing the previous number or going in on Month Day 1 and hand entering that number into a chart so it updates the dashboard widget.

Any suggestions would be sincerely appreciated!

Thank you!