Data Validation on blank cells

[Guest]

Hello,

I have a worksheet that I track my reqs on, column b is the req# column.
I use this sheet daily to add new reqs to, I would like to add validatioin
to the blank cells in column B so when I type in a new req# it will tell me
if any of the preceeding cells have that req# already in it so I do not have
duplicate req. numbers.

What would the best suggestion be for this..?

Thank you.
Lou

 

[Peo Sjoblom]

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