vlookup or sumproduct formula for 2 columns data validtion

[JC]

need to flag in 3rd column when data based on 2 other columns is repeated

I have two columns where data needs to be validated based on the two columns.

Trying to get the Sumproduct() to do it for me but its not coming back right

Column
A B
Customer group Client
Employer Group-National 0001
Key Accounts 0001
Health Plans 0001
Employer Group -Systemed 0001
Other Customer Group 0001

I want to setup a column PC
With formula flag to let user know if they are repeating the group/client
combination
The group should be one of the ones listed and the client can be any client.

customer group can repeat only for another client number

Can you help me.

 

[Bernard Liengme]

Have a look at:
http://www.mvps.org/dmcritchie/excel/duplicates.htm

http://www.cpearson.com/excel/duplicat.htm#Replacing