No VBA required. Suppose it's column B which yuo want to limit to unique
values. Select the whole column, use Data/Validation, select Custom from the
"Allow" dropdown, enter this formula:
=COUNTIF(B:B,B1)=1
and perhaps click the Error Alert tab to supply a message when a duplicate
value is entered.

"Michael" wrote:

I am looking for a way to limit a named range to unique values. So
that if a value is entered that already exists in the range the value
that already exists would become empty and the new location would hold
the unique value.

I got something sort of working with the selection change event but it
took too long to cycle through each cell in the range to make sure it
did not equal the target value. was not pretty. The range is only
like 50 cells.

I am looking for advise on how to make it work.

Thanks
.