=SUM(IF(COUNTIF($A$1:$A$100,$A$1:$A$100)1,0,1))

This is an Array** formula. Press CTRL+SHIFT+Enter to commit the formula to
the cell. This is assuming data is in all 100 cells.
--
John C


"Alan" wrote:

How can I take a range (a1:a100) that ISN'T sorted and find the number of
unique entries?