I'm trying to use a formula to calculate a 3 month running average of a data set that will expand over time...and I don't want to update the formula every month. I need the formula to calculate the average of the 3 RIGHT most, non-blank columns within the data set.

My data set uses 24 columns (2 years in total, 1 column for each month) with a numeric value (including zero).

I've got a formula that I think is close, but it's not getting me there:

AVERAGE(OFFSET(INDEX(H10:AD10,,COUNT(H10:AD10)),,-1,1,3))

The last 5 columns contains the values 2106, 1665, 0, 895, 3427...for a which 3 month average would be 1440.67, but the formula is returning 2161.

I'm stuck...any suggestions?