IBP Weekly indices calculation logic

Tthere is requirement to calculate Weekly indices based on past two years sales history. The logic requested is as below:

• W1 Indices Calculation : Average ((X1W1/Sum(X1W1:X1W5),(X2W1/SUM(X2W1;X2W5)). Similary W2 W3 etc should be calculated

  This is required across the future buckets. This calculation will be required at WK/PRODUCT/LOCATION/CUSTOMER Catch is that the summation of week values should be restricted within that month

  Periodw1w2w3w4w5No. wksFinal POD qty prior 2yr (X1)2016161612Final POD qty prior yr(X2)2020202020

  Let me know any suggestion how to achieve this or any confusion with the requirement.