请高手来帮看看这段代码如何提高效率

我是在ACCESS的VBA里编程。数据库就用的ACCESS 2003，VBA的代码也是直接就写在同一MDB里。用的是DAO.

下面的代码是用来一次性计算层次百分比。关于层次百分比的概念我解释在这个帖子里：http://blog.csdn.net/slowgrace/archive/2009/04/16/4084636.aspx。下面这段代码对一个有两万多条记录的节点表进行计算时需时20分钟，如果用注释掉那个则需时16分钟。注释掉的部分和没注释掉的部分的区别在，注释掉的用的是DAO的edit和update方法，没注释掉的用的是update语句。我真没想到直接用update语句还慢。但不管是哪种都太慢了，是吧？请各位前辈高人指点：

'算从lngrootid这个根节点开始的所有子节点（含根节点）的金额和百分比

'并把计算结果放在节点表的相应字段里

'返回根节点的值

Public Function CalValuePercent(strNodeTable As String, lngRootId As Long) As Single

    On Error GoTo Err_CalValuePercent

    

    Dim rstNode As DAO.Recordset, rstDetail As DAO.Recordset

    Dim strSql As String

    Dim sngValue As Single

    Dim blnNoChild As Boolean

    

    sngValue = 0

    

    '得到每个孩子的值(递归)并累积自己的值（等于所有孩子的值的总和）

    strSql = "SELECT lngNodeId FROM " & strNodeTable & " WHERE lngFatherId = " & lngRootId

    Set rstNode = CurrentDb.OpenRecordset(strSql)

    If rstNode.EOF Then

        blnNoChild = True

    Else

        blnNoChild = False

        While Not rstNode.EOF

            sngValue = sngValue + CalValuePercent(strNodeTable, rstNode.Fields("lngNodeId")) '递归调用

            rstNode.MoveNext

        Wend

    End If

    rstNode.Close

    Set rstNode = Nothing

    

    '将自己的值记录到数据库里

    If blnNoChild Then

        strSql = "SELECT strDetailTable, lngDetailId FROM " & strNodeTable & " WHERE lngNodeId = " & lngRootId

        Set rstNode = CurrentDb.OpenRecordset(strSql)

        If IsBasicTable3Db(Nz(rstNode.Fields("strDetailTable"))) Then '如果是基础节点，则从基础表抄value过来

            strSql = "SELECT sngValue FROM " & rstNode.Fields("strDetailTable") & " WHERE lngId = " & rstNode.Fields("lngDetailId")

            Set rstDetail = CurrentDb.OpenRecordset(strSql)

            sngValue = Nz(rstDetail.Fields("sngValue"))

            rstDetail.Close

            Set rstDetail = Nothing

        End If

        rstNode.Close

        Set rstNode = Nothing

    End If

    strSql = "UPDATE [" & strNodeTable & "] SET [sngValue] = " & sngValue & " WHERE lngNodeId = " & lngRootId

    CurrentDb.Execute strSql

'    strSql = "SELECT lngNodeId, strDetailTable, lngDetailId, sngValue FROM " & strNodeTable & " WHERE lngNodeId = " & lngRootId

'    Set rstNode = CurrentDb.OpenRecordset(strSql)

'    If blnNoChild And IsBasicTable3Db(Nz(rstNode.Fields("strDetailTable"))) Then '如果是基础节点，则从基础表抄value过来

'        strSql = "SELECT sngValue FROM " & rstNode.Fields("strDetailTable") & " WHERE lngId = " & rstNode.Fields("lngDetailId")

'        Set rstDetail = CurrentDb.OpenRecordset(strSql)

'        sngValue = Nz(rstDetail.Fields("sngValue"))

'        rstDetail.Close

'        Set rstDetail = Nothing

'    End If

'    rstNode.Edit

'    rstNode.Fields("sngValue") = sngValue

'    rstNode.Update

'    rstNode.Close

'    Set rstNode = Nothing

    

    

    '计算每个孩子的百分比

    If Not blnNoChild Then

        strSql = "UPDATE [" & strNodeTable & "] SET [sngPercent] = " & _

            "IIF(" & sngValue & "=0, 0, [sngValue]/" & sngValue & ") " & _

            "WHERE [lngFatherId]=" & lngRootId

        CurrentDb.Execute strSql

       

'        strSql = "SELECT lngNodeId, sngValue, sngPercent FROM " & strNodeTable & " WHERE lngFatherId = " & lngRootId

'        Set rstNode = CurrentDb.OpenRecordset(strSql)

'        While Not rstNode.EOF

'            rstNode.Edit

'            If sngValue = 0 Then

'                rstNode.Fields("sngPercent") = 0

'            Else

'                rstNode.Fields("sngPercent") = rstNode.Fields("sngValue") / sngValue

'            End If

'            rstNode.Update

'            rstNode.MoveNext

'        Wend

'        rstNode.Close

'        Set rstNode = Nothing

    End If

    

    CalValuePercent = sngValue

    Exit Function

    

Err_CalValuePercent:

    Stop

    Debug.Print ERR.Description

    Resume

End Function