Excel: Formula to Average lowest 10 of most recent 20 values

I have columns of golf scores (by person and date of round) varying from 1 score to 30 scores and constantly being added to. I need a formula at the bottom to average the lowest 10 scores from the most recent 20. Some columns have many blanks, some are very few. And if a column has less than 20 scores, it needs to average whatever is available. Thanks!

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This thread is current as of November 17, 2014.

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