Updating Cell according to Date Entry

I’m looking to automate a stage process, where when a date is entered in a specific column it updates a cell with a specific number.

I’ve mocked this out, so that in the scenario, the progress column should update automatically.

It was excellently suggested by a colleague to simply add up the columns to replicate the stage, but this isn’t always going to be the case that each date is filled in.

Any suggestions welcome please!