I would like to use the 10 lowest scores from the last 20 rounds played. I
dont want to consider the weeks not played.

So I may have a row with 26 cells and with 2 cells that are blank (or 0)
because the golfer did not show up to golf those weeks. I would like to go
from right to left in the row and consider the first 20 cells that are not 0
or blank and then take the lowest 10 of these 20 scores and average those 10
cells. (The reason for going right to left is that I will add a new score to
the end of the row when the golfer play another round the following week
(after the 45 in the example below)

For example €“ scores over the past 25 weeks:


41, 40, 42, 38, 46, 44, 41, -, 39, 40, 41, 40, 43, 42, 41, 40, 42, -, 40,
41, 42, 38, 40, 42, 45


I would like to begin considering the score of 45 in week 25 and consider
the previous 20 nonzero scores going the left (in this example it would take
be to the 38 in week 4). From those 20 nonzero scores, take the 10 lowest
scores and develop an average. Assuming the golfer showed-up in week 26 I
would repeat the process beginning with the score made in week 26 and going
to the 46 in week 5.


Other considerations:

For players with between 10 & 20 scores, take the lowest 10 nonzero scores
and average them. For players with less than 10 scores, take an average of
all nonzero scores.

Please help with the formula to accomplish this