Help with related records status and views

All of my customers have their own service month, which 95% of the time doesn’t change year on year, at the moment I have a date field with 1st of that month entered which is hidden, I also have a text field with the name of that month, which is shown in my “Customer Detail View” there is probably a better way of doing this, but thats for another time.

My question is I have a slice for Customers by month, so at the start of the month I want to see all the customer in a list, as I add job records for each customer and complete them I want the customer to be removed from the list, so when I get to the end of the month and the list is empty I know I have completed all the jobs required.

This is what I have to show all customer with a service Month of May with zero related jobs…

AND([Service Month] = “May”, ISBLANK([Related Jobs]))

and I set up a workflow so that when I set a job status to complete, it copies the row to a new tabled named completed jobs and then deletes the row in related jobs, meaning it would then appear in the view again as per above expression, the issue with that is, if I completed that job say in the first few days of the month, it would then show back up in the first view, which I don’t want, I would only need it to show up in that view again the following year.

Another thought would be to use formatting to have all the customer names show up in red to start with and once a job has been completed, show green, but the same issue would come up of when I have the system turn the customer name back to red for the following year.

I hope that makes sense, maybe there is another way of looking at it?

Any ideas are welcome.