Average of Last 3 weeks in current period at request level

[mansivachhan]

Hello Experts,

We have one requirement, where in we want to calculate "Hist AR Adj" key figure in current bucket(Weekly) at Planning level Week, Product ID, Location ID, Model ID level.

Base Planning Level of KF "Hist AR Adj" is Technical week, Product ID, Location ID, Child Product ID and Model ID.

Calculation formula is as below.

If "Hist AR adj" Key figure is blank in current week, we need to take average of previous 3 weeks.

Hist AR Adj(W0) = Average(Hist AR Adj(W-1),Hist AR Adj(W-2), Hist AR Adj(W-3)).
So here Avg(0.3,0.1,0.05) = 0.15.

Kindly suggest how to get this calculation at current period.

Thanks.