Vlokupand duplicates

[annegrey]

Hi

I need some help please!

I have a list where mobile phone numbers are entered. I have a colums next to this field where I would like to write a furmula that will check the mobile number in the previous column and return a "Yes" if the mobile number has been used before and a "N"o" if it has not been used before.

Thanks in advance

AG

 

[Bozacke]

Try =IF(ISERROR(VLOOKUP(B1,A:A,1,FALSE))=TRUE,"No","Yes")

where B1 is the number and colum A is the list of previous numbers.