Dynamically Find the previous 3 month average

[Jun Villanueva]

Hi, I am attempting to get the last 3 months average of out%. so far could not find any sample that suit for my requirement. Appreciate any help that could be provided.

There's a multiple column that i need to consider. I have to add the current month good% and the out% in the calculation to get the forecast.

This code gives me an error and the values reflected in the column is incorrect. Sum([out]) / Sum([in]) over (LastPeriods(3,[month])).

Please find below sample result and data. THank you in advance.