Formula to FIND DUPLICATE DEBIT AND CREDITS

[Joe H.]

I am trying to make a bank reconciliation template. I need to know the
amounts in a column that are duplicates. The duplicates may be a "credit"
amount or a "debit" amount in the same column. I would like to mark them both
as duplicates.
I would like to see for example:
A B
1234.00 duplicate
2345.00
3456.00 duplicate
4567.00
-1234.00 duplicate
-3456.00 duplicate

Thanks!

 

[Toppers]

=IF(COUNTIF($A$1:$A$6,A1)=COUNTIF($A$1:$A$6,-A1),"Duplicate","")

 

[Joe H.]

Thank you very much. Is there also something that could be added so that
"blank" cells would not have the "duplicate" printed?