Private Sub Worksheet_Activate()
Dim f As Worksheet: Set f = Sheets("TELEPHONIE")
Application.ScreenUpdating = False
ComboBox1.Value = Null
ComboBox1.List = f.Range(f.[A2], f.Cells(Rows.Count, 1).End(3)).Value
ComboBox2.Value = Null
ComboBox2.List = f.Range(f.[B2], f.Cells(Rows.Count, 2).End(3)).Value
ComboBox3.Value = Null
ComboBox3.List = f.Range(f.[H2], f.Cells(Rows.Count, 8).End(3)).Value
Application.ScreenUpdating = True
End Sub