unique CONCATENATE

[ccsmith]

I have some data in columns A-B-C which can't be modify. I nned a CONCATENATE function as way as I indicated in column E in zhe uploded sample file. I can create a simple CONCATENATE function but it not makes the right result. Please check the sample file and give me some suggestion to get the required result. Thanks.

[DonkeyOte]

Using your sample

D3:
=LOOKUP(9.99E+307;$A$3:$A3)&"/"&$C3
copied down

[ccsmith]

DonkeyOte: Thank you. It's working.