help with formula

[Soth]

A B C-count

10 A
10 A
10 A 2 Dup
20 B
20 C

There are duplicates numbers in Column A and B. How do you write a formula
to look up all fields in all columns for any possible duplicates place and
count the value in column c.

Many thanks,
Soth

 

[Ms-Exl-Learner]

If your data starts from 2nd Row then use this formula in C3 cell
=IF(AND(B2<>B4,COUNTIF($B$2:$B3,$B3)-1>1),COUNTIF($B$2:$B3,$B3)-1&" DUP","")

If your data starts from 1st Row then use this formula in C2 cell
=IF(AND(B1<>B3,COUNTIF($B$1:$B2,$B2)-1>1),COUNTIF($B$1:$B2,$B2)-1&" DUP","")

Change the column reference B to A if required.

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