Amber,
A simple way would be to use something like this, call it form the workbook
open event.
Sheets("Sheet1").Range("A1").Value = _
Sheets("Sheet1").Range("A1").Value + 1

For other ways to do this or if this is going to be used in a temple have a
look here
http://www.mcgimpsey.com/excel/udfs/sequentialnums.html


--
Paul B
Always backup your data before trying something new
Please post any response to the newsgroups so others can benefit from it
Feedback on answers is always appreciated!
Using Excel 2002 & 2003

"Amber" wrote in message
...
How can I set up on invoice on excel to where I get automatic sequential
numbering each time the spreadsheet is opened?