Excel VBA code-sequential numbering

[Jegacats]

Would someone please tell me a code I can use for sequential numbering ?

 

[zacemmel]

Sequential numbering for what?

 

[Jegacats]

Sequential numbering used to number invoices,
time sheets etc...

 

[Jegacats]

I can't believe no one has a solution.
I know I'm not very clear on what I am looking for. I will try to give a more concrete example.

I have a template (My expense report)When I open it, I would like it to have the current expense report number.
Ex : If the last number I used was 10, I would like the next one I make to be 11.

Thanks for any suggestions.

 

[zacemmel]

Private Sub Workbook_Open()
Range("a1").value=range("a1").value+1
End Sub

 

[Jegacats]

Thank you. This works fine.
I opened the template, copied the code,saved the template. I tested the template.
I did "file" new and there it was, the number changed . I filled out the form and saved it with a new name and as an .xls

The next time I did file new, the number did not change..