Using Excel 2003. I have a ws with 3000+ rows of data that I need to find at
least the first instance of a duplicate. I copied and modified the following
formula from http://www.cpearson.com/excel/Duplicates.aspx, however I am
getting incorrect results:
=IF(COUNTIF($A$1:$A$3500,A1)=1,FALSE,COUNTIF($A$1: A1,A1)=1)

In some cases, the fomula gives the correct results, other areas it will
give the result of "True" although the entry is unique, other areas the
result is "False" and there are at least 3 entries in the column. Following
are samples of the results:

This section the results are OK:
Column A B C D
4536057761268403 1 50000 TRUE
4536057761268403 1 40000 FALSE
4536057781990705 1 30000 FALSE
4536057811016703 1 50000 TRUE
4536057811016703 1 40000 FALSE
4536057811645204 1 50000 TRUE
4536057811645204 1 40000 FALSE
4536057811645204 1 30000 FALSE

This section I get True on a unique entry:
5047429900014284707 21 112800 FALSE
5047429900014292510 1 30000 TRUE
5047429900014294003 21 122000 FALSE

This section I get False on a multiple:
5047429900014294904 1 42000 FALSE
5047429900014294920 21 120000 FALSE
5047429900014294920 21 35000 FALSE
5047429900014294920 21 115500 FALSE
5047429900014295273 1 48200 FALSE

Am I using the formula incorrectly, or is there simply too much data to
compare that it doesn't work on every row? The results, correct and
incorrect, are mixed throught the worksheet. All numbers in Column A are
formatted as 'Text'.

Any help would be appreciated, I have a large document I am trying to
finalize.
Thanks!
--
Linda