Formula to List Rows for Duplicate Cells in a Column

[pbornemeier]

For a given column, this helper-column formula will indicate if the text in an entire cell has not appeared previously with "First". If cell text has appeared before, display the row where it first appeared:

=IF(ROW(F3)<>MATCH(F3,F:F,0),MATCH(F3,F:F,0),"First")
 
Example:
Row Data Helper
1   A    First
2   B    First
3   C    First
4   A    1
5   C    3

Is there a formula that would show each row where duplicate text appears in the helper column?

Example:
Row Data Helper 
1   A    1,4
2   B    2
3   C    3,5
4   A    1,4
5   C    3,5

The real-life data runs about 1500 rows with no more than 20 duplicates.

Organization involved wants to avoid the various VBA solutions.

 

[Marcelo Branco]

This works for the 5 rows shown, but it would be useless for a 1500 row list:

=SUBSTITUTE(INDEX((--($A$2:$A$6=$A2)*ROW($A$2:$A$6)),1)&","&INDEX((--($A$2:$A$6=$A2)*ROW($A$2:$A$6)),2)&","&INDEX((--($A$2:$A$6=$A2)*ROW($A$2:$A$6)),3)&","&INDEX((--($A$2:$A$6=$A2)*ROW($A$2:$A$6)),4)&","&INDEX((--($A$2:$A$6=$A2)*ROW($A$2:$A$6)),5)&",","0,","")

Yes, i still think you'll have to use VBA (UDF for concatenate)

M.