Formula for an Average that Reduces each Month

Hello you wonderful excelthusiests! I’m wondering if something is possible that goes beyond my own personal mediocre excel skills:

I have a goal # of widgets I need to meet for the year. I currently track how many widgets I make each month, what my YTD total is, and how many widgets I have left that I need to make before the year is out. What I would love to have is some kind of formula for: how many widgets per month I need to make in order to reach my goal by the end of the year. This number obviously changes as my actual widget production varies from month to month, and the number of months left reduces by one at the end of each month. I would like a box that automatically adjusts my needed widgets/month as I fill in the months through the year.

Edit to add: it’s excel Microsoft 365 Apps for Business. Version 2604. It’s my work computer and I don’t really know anything more than what the “product information” page says.