Hi Jo
If only numeric values:
=SUM(N(FREQUENCY(A2:A12,A2:A12)0))

See Chip Pearson's http://www.cpearson.com/excel/Duplicates.aspx

HTH
Cordially
Pascal


"Jo" a écrit dans le message de news:
...
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