Comboboxen in Abhängigkeit füllen

bsp.
in combobox1 wird "a" ausgewählt --->
dann soll in Combobox2 "y" stehen

wird in combobox1 "b" ausgewählt --->
dann soll in combobox2 "x" stehen

usw.

Private Sub UserForm_Initialize()
i1 = "PPC5112"
i2 = "PPC5112 TC"
i3 = "PPC5212"
i4 = "PPC5115"
i5 = "PPC5115 TC"
i6 = "PPC5315"
i7 = "PPC5515"
i8 = "PPC5318"
i9 = "PPC8715"

ComboBox1.AddItem (i1)
ComboBox1.AddItem (i2)
ComboBox1.AddItem (i3)
ComboBox1.AddItem (i4)
ComboBox1.AddItem (i5)
ComboBox1.AddItem (i6)
ComboBox1.AddItem (i7)
ComboBox1.AddItem (i8)
ComboBox1.AddItem (i9)

End Sub

Private Sub ComboBox1_change()
ii1 = "12 Zoll; 800 x 600; Touchscreen"
ii2 = "15 Zoll; 1024 x 768; Touchscreen"
ii3 = "15 Zoll; 1024 x 768"
ii4 = "18 Zoll; 1280 x 1024; Touchscreen"
iii1 = "Sonderausstattung"

If ComboBox1 = ComboBox1.List(i1) Then
ComboBox2 = (ii1)
ComboBox2.AddItem (iii1)
Else
ComboBox2.Clear
ComboBox2 = ""
End If

If ComboBox1 = ComboBox1.List(i2) Then
ComboBox2 = (ii2)
ComboBox2.AddItem (iii1)
Else
ComboBox2.Clear
ComboBox2 = ""
End If

'----zweiter versuch mit select case-----
'Select Case ComboBox1 <= (i9)
'Case ComboBox1 = (i1)
'ComboBox2 = (ii1)
'ComboBox2.AddItem (iii1)

'Case ComboBox1 = (i2)
'ComboBox2 = (ii2)
'ComboBox2.AddItem (iii1)

'Case Else
'ComboBox2.Clear
'ComboBox2 = ""
'End Select

End Sub

Danke für eure Hilfe
Carsten