A solution to a similar question to this one has previously been provided:
This time, what is needed is the average value of the 30 years of "n" data leading up to and including the year listed in the "year" field (Column B). This result should be included in the "n_30yr_avg" field (Column C).
The first 52 values for "n_30yr_avg" have been solved manually in the attached worksheet.
Is there a solution that would provide this calculation for all records?