请教:树中的Refresh何时使用?

请先帮我检查下面的程序:(用了选项组和树状两个控件)

请教:1.[Me.TreeView3.Refresh用和不用运行结果都好象正确且没区别.]

     2.我纯属死看书型自学者,不正确,特别是不规范的地方肯定会有很多,请帮多多指教,万分感谢!

Option Compare Database
Dim NODX As Node
Dim RS As New ADODB.Recordset
Dim I As Integer
Dim ABC As String

Private Sub Form_Load()
Set NODX = TreeView3.Nodes.Add(, , "爷", "计划中指示单", 1, 2)
'ABC = "SELECT 客户指示单.指示单号 FROM 客户指示单 WHERE (((客户指示单.状态)=" & "0" & "))"
'上句不对!
'Me.TreeView3.Refresh
End Sub

Private Sub Frame1_AfterUpdate()
For I = TreeView3.Nodes.Count To 2 Step -1
TreeView3.Nodes.Remove (I)
Next I
Select Case Frame1.Value
Case 1
'******下句0的两边可加可不加双引号!******
ABC = "SELECT 指示单号 FROM 客户指示单 WHERE 状态='" & 0 & "'"
RS.Open ABC, CurrentProject.Connection, adOpenKeyset, adLockOptimistic
For I = 0 To RS.RecordCount - 1
Set NODX = TreeView3.Nodes.Add("爷", TVWCHILD, "父" & RS.Fields("指示单号"), RS.Fields("指示单号"), 1, 2)
RS.MoveNext
Next
'Me.TreeView3.Refresh
Case 2
ABC = "SELECT 指示单号 FROM 客户指示单 WHERE 状态='" & 1 & "'"
RS.Open ABC, CurrentProject.Connection, adOpenKeyset, adLockOptimistic
For I = 0 To RS.RecordCount - 1
Set NODX = TreeView3.Nodes.Add("爷", TVWCHILD, "父" & RS.Fields("指示单号"), RS.Fields("指示单号"), 1, 2)
RS.MoveNext
Next
'Me.TreeView3.Refresh
Case 3
ABC = "SELECT 指示单号 FROM 客户指示单 WHERE 状态='" & 2 & "'"
RS.Open ABC, CurrentProject.Connection, adOpenKeyset, adLockOptimistic
For I = 0 To RS.RecordCount - 1
Set NODX = TreeView3.Nodes.Add("爷", TVWCHILD, "父" & RS.Fields("指示单号"), RS.Fields("指示单号"), 1, 2)
RS.MoveNext
Next
'Me.TreeView3.Refresh
End Select
'Me.TreeView3.Refresh
RS.Clone
Set RS = Nothing
End Sub