Marilinn,
Please do the following steps:
Suppose that you have your list from A1 to A10, from the Data menu choose
validation and from Allow drop down list choose CUSTOM and in the formula bar
put this:

=Countif($A$1:$A$10,A1)=1

Let me know if this works.

Daoud Fakhry

"marilynn" wrote:

I'm trying to create a schedule for weekend duties, without repeating names
of the people involved, so that more than one job is not assigned to a person