Put this formula next to the numbers

=COUNTIF(A:A, A2)=1

assuming your data is in column A, and starts in A2.

It will return TRUE for each unique number, or FALSE for each item that is
repeated.

--
Regards,

Juan Pablo González
Excel MVP

"Jonibenj" wrote in
message ...

How can I run a check on a column of figures to make sure that I haven't
doubled-up any of them? In other words, each number is only allowed to
be entered once, so if any of them appear more than once, I want to be
notified at the bottom.

Jonathan


--
Jonibenj
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