Formula that recognizes duplicates

[Guest]

I need a formula that tells me if there is a duplicate within the same
column. I have no idea how to go about this. I am wanting to enter in
Product ID numbers and if there is a duplciate I need to be warned. I would
appreciate any help anyone can give - Thanks!

 

[RagDyer]

Check out this web site of Chip Pearson's.

Scroll down to the "D's", and see all the pages pertaining to duplicates.

http://www.cpearson.com/excel/topic.htm
--
HTH,

RD
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Please keep all correspondence within the Group, so all may benefit!
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[JE McGimpsey]

Take a look here:

http://cpearson.com/excel/duplicat.htm

and

http://cpearson.com/excel/NoDupEntry.htm

 

[Guest]

This solution does not allow me to check for existing numbers. Lets say that
I have a list of numbers but change a number somewhere near the top. Data
Validation does not check that number.

 

[JE McGimpsey]

Which of the many solutions on those two web pages are you talking about?

If the one at http://cpearson.com/excel/NoDupEntry.htm, did you use
absolute references for your input range?

E.g.,

=COUNTIF($A$1:$A$50,A1)=1

not

=COUNTIF(A1:A50,A1)=1

????

Select column A, inputIn article

 

[Guest]

the no dupentry does not work on numbers that are already entered. It only
checks against the numbers that are pre-existing. I want to have a list and
without entering any more numbers check to see if there are duplicates in the
exising list. I hope that makes sense.

 

[JE McGimpsey]

That's what several of the formulae in the first reference I listed does
- it checks to see if there are duplicates in the existing list. Look
under "Testing For Duplicate Entries"

 

[Guest]

Thank you very much!

That's what several of the formulae in the first reference I listed does
- it checks to see if there are duplicates in the existing list. Look
under "Testing For Duplicate Entries"