Hi @James_Thomas ,
I’ve created an excel file based on the data you show.
Then to calculate the Lag X Forecast I’ve used this kind of formula each time
The final result is that :
All the results aren’t shown because I’ve stopped the excel on April 2021 submission date.
Here is the files :
Book3.xlsx (9.7 KB)
Untitled4.pbix (48.3 KB)
I hope it will help you.
Best regards,
Joaly