Samantha,

Highlight A2:A20
From Data | Validation:
Allow = Custom
Formula: =COUNTIF($A$2:$A$20,A2)=1


Rob



"Samantha James" wrote in message
om...
Hi,

I am struggling to find a method prevent users entering
duplicate data to a coulumn.

The requirement is quite simple -- check
if the same cell value is already found in the column to
which data is currently being entered.

For instance, when entering data to cell A8, I need
to check if the the same value is already found in the
cells ranging from A2 to A20.

This is just to prevent users entering dupliate data.

Could someone kindly give me any sample code or hint ?

Thank you very much
Samantha