Calculate averages over a dynamic number of months.

[AlBoo8749]

I have a table that I want to calculate the average of a group of percentages over a certain number of months depending on the development period. In the Excel file that I uploaded the variables are arranged in triangle fashion. To the left are the end of dates and on the top are the development periods. I need to calculate the averages for 12 months prior to the date and I need to calculate the averages for the remaining months after the date. The average percentages should match the table to the right of the triangle. Is there an easy way to do this?

[Kushal_Chawda]

@AlBoo8749  how those % are calculated? Is it a available as a value in column of the table?  How your data look like in terms of row and columns? 

[AlBoo8749]

The data in the triangle are values in the columns.

The data in the other table with the headings 'Before' and 'After' are calculated from the data in the triangle. The calculation is depended on the number of months before and after a certain date. That date will change in the future so the number of months will calculated based on what months have data available.

I hope this answers your question.