I've searched through a lot of the previous posts here and have been unable to find code that will work for me. I'm a relative newbie.

I'm using Excel 2003 for a project log file that will only allow the user to type in a number that has not been "used" yet, in an effort to prevent duplicate project numbers.

I need some code that will check Column "C" starting in the second row.
Then highlight the duplicate, but not the first occurrence. There will only be numbers in column C, not including the header row.
Then pop up a message box that states the value in the message that says:
"The following number has already been taken " & cellvalue

I think that a "Worksheet_Change" type of setup might work but I'm not sure.
Nearly everything else I could find was to delete duplicates, and that's not useful for this application.

Any help is appreciated.

Thanks
Rolly