Need help w/ excel formula (duplicate entry)

[cl6120]

Hello,

I am not sure if this is possible but I would like
write a formula that would recognize a duplicate entry
under same column.

e.g., column A has heading of Sample ID# and
under is sample ID# in random order. If an entry
of ID is then made but if it is a repeat of the ID that was
previously entered, I would like to it to give some kind
of warning message.

Thank you.

 

[Dave Peterson]

You may want to read some of Chip Pearson's techniques for dealing with
duplicates:
http://www.cpearson.com/excel/duplicat.htm

Visit Chip Pearson's site for a Data|validation solution:
http://www.cpearson.com/excel/NoDupEntry.htm

 

[Mladen_Dj]

Use Data Validation. Go to Data->Validation, under Alow select custom, and
enter folowing formula:

=COUNTIF(A:A;A1)=1

Under Error Mesage create text you want to be displayed to user when he try
to enter ID# already in use.