Dear experts,

I've a range named "staff" which I have set a validation: List -- source =
INDIRECT($B$1). For the dropdown list, the users can select the staff name
within the range. However, in the meantime, I want to set another validation
to the range so that there is no duplicate entry: Custom -- source =
COUNTIF($C$C, C2)<=1. However, when I select the range and want to set
another validation, the first validation appears and seems I cannot input
another validation. Is there a way to do this? If yes, how? If no, please
advise is there other way to achieve this.

Thanks in advance.