Need formula creation

[Soth]

Hi

I need help with formula creation. I'd like to look and find number in
column A and B for duplicate numbers, then show its duplicate value or number
in colum C. Please see below example. Thanks

A B C
101 $10
101 $10 1
102 $20
103 $30
103 $30 2
103 $30
104 $40

 

[Commish]

Hi

I need help with formula creation.  I'd like to look and find number in
column A and B for duplicate numbers, then show its duplicate value or number
in colum C. Please see below example.  Thanks

A              B             C
101           $10
101           $10         1
102           $20
103           $30        
103           $30         2  
103           $30
104           $40

In C2, try this - then fill down.

=IF(COUNTIF($A$1:A2,A2)=1,"",1+MAX($C$1:C1))