Concatenate if already exist in Columns...

[edvavi]

I will like to add a letter "B" if there is already one. Let me explain in column A there is a list of companies I will like that in column C check for the whole column and if there is that company again then add the letter B at the end if not just paste the name of the company.column.PNG

I used =IF(A2=A:A,CONCATENATE(A2,"b")) but with this always put the "b" and I only want it if there is the company more than one.