不要钻牛角尖,思路开阔点,看如下代码;
Private Sub combo1_click()
Combo2.Clear 
Select Case Combo1.Text
    Case "广东"
        Combo2.AddItem "广州"
        Combo2.AddItem "深圳"
Case "山西"
    Combo2.AddItem "太原"
    Combo2.AddItem "榆次"
End Select
End Sub
Private Sub Combo2_Click()
  Dim Combotext     As String
  Dim i     As Integer
  Combotext = Combo2.Text
  For i = 0 To Combo2.ListCount - 1
          If Combo2.List(i) = Combotext Then
                MsgBox "是第   " & (i + 1) & "   项"
          End If
  Next
End Sub
Private Sub Form_Load()
    Combo1.AddItem "广东"
    Combo1.AddItem "山西"
End Sub