一個邏輯上的問題??(編號:4305)

Private Sub Combo3_Click()
Dim Rs As ADODB.Recordset
Dim MySql As String
Dim Cus As ADODB.Connection
Set Cus = New ADODB.Connection
  Cus.ConnectionString
= "Provider=Microsoft.Jet.OLEDB.4.0; " & _
"Data Source= C:\Cyuan\Cy.mdb;Persist Security Info=False"
   Cus.CursorLocation = adUseClient
   Cus.Open
     
  Set Rs = New ADODB.Recordset
  Select Case Combo3.Text
    Case "ALL"
      MySql = "select 簡稱 from 客戶基本資料 order by 客戶編號 "
    Case "01"
      MySql = "select 簡稱 from 客戶基本資料 where 客戶編號 like '01%' order by 客戶編號 "
    Case "02"
      MySql = "select 簡稱 from 客戶基本資料 where 客戶編號 like '02%' order by 客戶編號 "
    Case "03"
      MySql = "select 簡稱 from 客戶基本資料 where 客戶編號 like '03%' order by 客戶編號 "
    Case "04"
      MySql = "select 簡稱 from 客戶基本資料 where 客戶編號 like '04%' order by 客戶編號 "
  End Select
  
  Set Rs = Cus.Execute(MySql, , adCmdText)
  
  Do Until Rs.EOF
   Combo4.AddItem Rs!簡稱
   Rs.MoveNext
  Loop
  Rs.Close
  Set Cus = Nothing

End Sub
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這個程式有一個問題
例如我在combo3先選01
combo4就會跑出以01開頭的所有資料
可是當我再選擇02時
combo4的list卻沒辦法更新
這要如何解決呢??