Trying to build an excel budget tracker that automatically calculates updated monthly expenses as months occur.

I am trying to build a budget tracker that shows average expenses of various categories. I want to make it so it updates to calculate a new average, including the next month once that month ends and not include months that have not happened yet. Using the average function includes all the months I currently have included within the budget tracker, which obviously makes the average much lower than it should be. I tried using EOMONTH, but could not find a way to change which months it includes in the calculation without me having to update it monthly.