select the column where you will enter the SSN
go to Data Validation and enter
=COUNTIF(A$1:A$1000,A2)<2
this will give an error message whenever a SSN is repeated.


"repeat" wrote in message
...
I have social security numbers in a column. I cannot have a repeat of any
of
these numbers. Is there a way to set it up so it alerts me if I have two
of
the same social security numbers in that column?