Code for select multiple elements in excel drop list

Private Sub Worksheet_Change(ByVal Target As Range)

'Code by Sumit Bansal from https://trumpexcel.com
' To make mutliple selections in a Drop Down List in Excel

Dim Oldvalue As String
Dim Newvalue As String
Dim num As Integer

On Error GoTo Exitsub
If Target.Address = "$E$2" Then
    If Target.SpecialCells(xlCellTypeAllValidation) Is Nothing Then
    GoTo Exitsub
    Else: If Target.Value = "" Then GoTo Exitsub Else
        Application.EnableEvents = False
        Newvalue = Target.Value
        Application.Undo
        Oldvalue = Target.Value
        If Oldvalue = "" Then
            Target.Value = Newvalue
        Else
            num = InStr(Oldvalue, Newvalue)
            If num = 0 Then ' If the element selected isnt already on the selected list
              Target.Value = Oldvalue & ", " & Newvalue
            ElseIf num = 1 Then ' If the element is the first on the list
              If Len(Oldvalue) = Len(Newvalue) Then ' If the element is the only element selected
                Target.Value = Replace(Oldvalue, Newvalue, "")
              Else                                  ' If the element is not the only element selected
                Target.Value = Replace(Oldvalue, Newvalue & ", ", "")
              End If
            ElseIf num > 1 Then  ' If the element is not the first
              Target.Value = Replace(Oldvalue, ", " & Newvalue, "")
            End If
        End If
    End If
End If
Application.EnableEvents = True
Exitsub:
Application.EnableEvents = True
End Sub