Take a look here:

http://www.mcgimpsey.com/excel/sequentialnums.html


In article <1F2F7A29-7316-401D-8D9D-27F75B417852@microsoft.com>,
"jo_9865" <jo_9865@discussions.microsoft.com> wrote:

> Does anyone know of a way to automatically insert the next sequential
> reference number into a form in excel.
>
> I would like a Purchase Order number to be automatically generated so there
> is no chance of the same number being used twice. Each purchase order is
> currently created on separate excel workbooks and a number is currently
> entered each time.
>
> Has anyone got any ideas as to how to solve this or is there another way to
> do this perhaps using Access?