Avoid duplicate data in another sheets at same workbook

Dear All;

I have already reviewed the post started from speedingpenguin regarding "Avoid duplicate entries across the worksheets" but I need some clarifications from Marcol or any other experts.

I was trying to apply the guidelines what you have given through above posts but it doesn't work properly. Could you advice me in this regard?

I have attached the excel file here.

Thanks in advance.

Originally Posted by CK76

Doesn't tell us much on your requirement or how it's not working.


At any rate... From what I can tell, the formula in Column B is working as intended.

But you have wrong cell reference in your validation formula. In Cell A2 you have validation formula of =COUNTIF(OldNum,A3)=0

You should enter =COUNTIF(OldNum,A2)=0 and copy down.

Thanks a lot for your swift response.

It's working well.