How do I keep duplicate text from being entered in an excel file?

[Ed Green]

I am entering product names in excel (in the hundreds) and I would like to
have excel check that as I enter a name it has not already been used.

 

[Per Jessen]

Hi

Select the column with product names, and goto Data > Validation > Allow:
Custom > Formula: =CountIf($A:$A,A1)=1

Hopes this helps
...
Per

 

[Jim Thomlinson]

You can use data validation with a custom formula. To restict the entries in
Column A

Select Column A
Select Data -> Validation | Custom
Add this formula
=COUNTIF(A:A, A1) = 1
Select Ok

Column A should now be restricted to unique entries.