Save a the same workbook but add a variable number at the end

Maybe:

Sub swade730()
Dim file As String, file2 As String
file = Left(ActiveWorkbook.Name, Len(ActiveWorkbook.Name) - 5)
file2 = Left(Right(ActiveWorkbook.Name, 5), 1)
ActiveWorkbook.SaveAs file & file2 + 1 & ".xlsx"
End Sub