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=SUM(IF(A1:A30<"",1/COUNTIF(A1:A30,A1:A30)))
Jo wrote:
Hi,

Say you have in column A this:

Order No
24
24
24
24
123
123
123
123
123
75
75

and so on. It means that we have 3 orders (i.e., 24, 123, and 75). How
can caculate this? I mean what formula can be used to do so?

Thanks,
Jo