Try this:

=IF(COUNT(B:B),AVERAGE(OFFSET(B2,COUNT(B:B)-1,,MAX(-COUNT(B:B),-30))),"")

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Biff
Microsoft Excel MVP


"~slacker~" wrote in message
...
no empty cells in the range.

it doesn't take long to get over 30 values but if it were less than
thirty then i'd want to average the 20 or whatever values that there
were.