Hi Excel Savants!

Im getting tired of manually updating my sum ranges in my Workbook. Heres the situation.

We r working with a 3 month average. So for example in august we need to take july june & may and divided by the numerator. The problem im facing is that i need to work back from august. All the formulas are on summary page referencing to the data worksheet.

Any thoughs on how to structure this so that each month i found possiably reference the current month on the summary page and have the sum function move and sum the prior 3 months? Maybe use index match ???

Any thoughts would be great, thanks!