If err.number... gives expected function or variable in Excel 2016

Ah, yes... That's called 'OverLoading'

An example. Say all your MsgBoxes have the same Icon, Buttons and Caption. Only thing that changes is the message. Write a Public Function 'MsgBox' that takes only the message as a parameter

Sub Test()

   If MsgBox("What to do") = vbYes Then
       ' Do something
   End If
End Sub

Public Function MsgBox(strMessage as String) as vbMsgBoxResult

    MsgBox = VBA.MsgBox(strMessage, vbQuestion + VBYesNo + vbDefaultButton2, "Standard Caption")

End Function

Your 'MsgBox' will run when called from Sub Test (or any procedure that does not qualify the call to MsgBox) as that will be the first MsgBox function found by the compiler, but that then calls the VBA MsgBox because it explicitly references the Library containing it - 'VBA.MsgBox'. Much the same as calling a procedure in another module in your code.