Je ne comprends pas quel est l'erreur dans ce code

Public Maj As Boolean
Private Sub OptionButton1_Click() 
  Maj = True
End Sub
Private Sub OptionButton2_Click() 
  Maj = False
End Sub
Sub Ecrire()
Dim i As Integer
  For i = 0 To ListBox1.ListCount - 1
      If Maj = True Then
          'Majuscule
          ListBox1.List(i) = UCase(ListBox1.List(i))
      Else
          'Majuscule
          ListBox1.List(i) = LCase(ListBox1.List(i))
      End If
  Next i
End Sub