Is there anyway of inserting an auto number in a cell like you can in Access.

I have tried using the code below, but its doing something different to what I want.

'/===============================/
Private Sub Worksheet_Activate()
Range("A1").Value = Range("A1").Value + 1
End Sub
'/===============================/

The spreadsheet I am working on requires the user to input helpdesk requests, and each request has a number which needs to be an autonumber. The same sort of thing when you add a record in access the autonumber gets inserted. Is there anyway that this can be done in Excel?

Thanks