rank a single or duplicate row and concatenate

[MarkJohn51]

Hi everyone..I'm wondering if anyone can help?

In my data A2 is the "Claim Number" which can sometimes be duplicated.

- If a Claim Number is not duplicated, I want to assign a "-1" in B2 (to later concatenate A2 and B2, in C2) example PRNWQ2456568-1

- If a Claim Number is duplicated, I want to assign a "-1", "-2", "-3" or "-4" etc for each row instance in B6 (to later concatenate A6 and B6, in C6) example PRNSF3459852-3


Please help with a simple solution for Columns, starting in B2 and C2.
Thank You !!

[CARACALLA]

	A	B
1	Claim Number
2	PRNWQ2456568	PRNWQ2456568-1
3	PRNWQ2567670	PRNWQ2567670-1
4	PRNSF3459852	PRNSF3459852-1
5	PRNSF3459852	PRNSF3459852-2
6	PRNSF3459852	PRNSF3459852-3
7	PRNSF3459852	PRNSF3459852-4
8	CSWRE4367101	CSWRE4367101-1
9	PRNSF1345616	PRNSF1345616-1
10	CSWRE4367101	CSWRE4367101-2

B2=IF($A2<>"",$A2&"-"&COUNTIF($A$2:$A2,$A2),"")

Copy down

[MarkJohn51]

Thanks Caracalla for the solution....this is working for my data for most number formats - though if 2 (or more) of my Claim Numbers are similar (except for the final digit) such as:

Column A
6115415918272985
6115415918272987

..The formula seems to be not recognising the final digit, in the above numbers "5" and "7"

therefore after running the formula, the data will result in...

Column B
6115415918272985-1
6115415918272987-2

As the Claim Numbers are different and have only one instance each, Column B should be:
6115415918272985-1
6115415918272987-1

I have tried various number formats for both Columns A and B (such as Custom, General, Text, Number) though this does not seem to work?

Please assist if possible.