J'ai trouvé la solution :
Private Sub LoadListMotif(strRange As String)
Dim ln As Long
ComboBox2.Clear
For ln = 2 To Feuil7.Range(strRange & "65535").End(xlUp).Row
ComboBox2.AddItem Feuil7.Range(strRange & ln).Text
Next
End Sub
Private Sub RefreshListMotif()
If (OptionButton3.Value And OptionButton5.Value) Then
LoadListMotif ("AC")
ElseIf (OptionButton3.Value And OptionButton6.Value) Then
LoadListMotif ("AD")
ElseIf (OptionButton4.Value And OptionButton5.Value) Then
LoadListMotif ("AE")
ElseIf (OptionButton4.Value And OptionButton6.Value) Then
LoadListMotif ("AF")
End If
End Sub