Cumulative calculation of total rows in a month and dividing by current month

[Jo5hua22]

Hi all,

I am trying to do a calculation wherein I have to perform cumulative calculation of total values (rows) in a month, followed by next month and then dividing the value with the current month

For example, there are 5 rows in January 2021, 3 rows in February 2021, 2 rows in March 2021. Then I need to add the 3 months and show in the visual of the fourth month with the value of (5+3+2)/ 4 (which is the 4th month in the year)

Can someone please help me out?

[lbendlin]

Please provide sample data in usable format (not as a picture) and show the expected outcome.