Preventing dupes in Excel.

So one of my users came to me for help, asking how they can prevent duplicate data from getting typed into there excel spreadsheets. I guess this chick has to keep a running tally of items and she didnt want dupes in there, and wanted to be warned if she tried to put in a dupe item, i did some goggling and came up with this:

In Excel:
From Data choose Validation.
Use Validation to enter a formula to catch entry of duplicate data.

Select cells A2:A20.
Choose Data, Validation.
Select the Settings tab.
In the Allow box, select Custom.

Note – The title of the third box in the dialog box changed to Formula.
Enter the following formula into the box: =COUNTIF($A$2:$A$20,A2)=1

Select the Error Alert tab.
In the Title box, enter duplicate.
In the Error message box, enter The value you entered already appears in the list.

Now the evil paperclip will popup and tell her she has a dupe, and wont let her put it in. Awesome huh! 🙂