Single Use Values in a Specified List

[msinex]

I have a column on a spreadsheet in which I want the only value to b
inputed are whole numbers between 1 and 240, but I don't want any valu
to be used more than once. I know that I can use data validation t
keep it to whole numbers, but is there a way to make sure each numbe
is only used once within this column? Thanks

 

[Biff]

Hi msinex!

Select the range to apply the data validation.

Use Data Validation. In the Allow dropdown, select Custom
and enter this formula: adjust the range reference in the
Countif function to suit:

=AND(A1>=1,A1<=240,A1=INT(A1),COUNTIF(A$1:A$240,A1)=1)

Biff