Can Excel warn me if a cell already contains entered information?

[Can Excel warn me if a cell already cont]

I'm using Excel to keep track of orders - each with a separate number. These
numbers are all in the same column. Can Excel warn me if another cell in the
same column already contains the information I'm trying to put in? Order
numbers consist of only four numbers, if it matters.

Thank you!

 

[Mike H]

Hi,

Select your column (A in my case) and then

Data|validation|Custom
enter the formula
=COUNTIF($A:$A,A1)<2

and if you want enter a suitable message and it will only allow unique values.

Mike

 

[Gord Dibben]

See Chip Pearson's site for preventing duplicates.

http://www.cpearson.com/excel/NoDupEntry.aspx


Gord Dibben MS Excel MVP