Sub Job_Number()
Dim Startcell As Range
' The fist job number cell
Set Startcell = Range("A2")
If IsEmpty(Startcell) Then
' First Job number
Startcell = 1
Else
' Next job number
With Cells(Rows.Count, Startcell.Column).End(xlUp)
.Offset(1).Value = .Value + 1
End With
End If
End Sub