淘宝API 中文sign问题

备注为英文时能正常调用，备注为中文的时候出错：<?xml version="1.0" encoding="utf-8" ?><error_response><code>25</code><msg>Invalid signature</msg></error_response>

望各位知道的大哥指点下，问题在什么地方？？？？

Public Function TRADES_MemoUpdate(ByVal AppKey As String, ByVal AppSevret As String, ByVal Session As String, _
                   ByVal Tid As String, Optional ByVal Memo As String = "", Optional ByVal Flag As Long = 0, Optional ByVal Reset As Boolean = False) As String
     '本函数：修改一笔交易备注
     Dim TaobaoAPIBasic As New TaobaoAPI_BasicModule.BasicClass
     Dim sURL, sTmp, Sign, strStatus, Api_Type As String
     Dim Url_Str As String
     Api_Type = Trim(APITypeStr(8))'//taobao.trade.memo.update

      Url_Str = Url_Str & "×tamp=" & Format(Now, "yyyy-MM-dd HH:mm:ss") ' UCase(TaobaoAPIBasic.GB2UTF8(Format(Now, "yyyy-MM-dd HH:mm:ss")))
      Url_Str = Url_Str & "&v=2.0"

      TRADES_MemoUpdate = ""

      If Trim(AppKey) = "" Then
         TRADES_MemoUpdate = "[ERR_XXTS]" & "不能缺少AppKey！"
         Exit Function
         Else
         Url_Str = Url_Str & "&app_key=" & AppKey
      End If

      Url_Str = Url_Str & "&method=" & Api_Type
      Url_Str = Url_Str & "&partner_id=top-apitools"
      Url_Str = Url_Str & "&session=" & Session
      Url_Str = Url_Str & "&format=xml"


      Url_Str = Url_Str & "&memo=" & UCase(TaobaoAPIBasic.GB2UTF8(Memo))
     ' Url_Str = Url_Str & "&flag=" & Flag
     ' Url_Str = Url_Str & "&reset=true"


      If Trim(Tid) = "" Then
         TRADES_MemoUpdate = "[ERR_XXTS]" & "不能缺少Tid！"
         Exit Function
         Else
         Url_Str = Url_Str & "&tid=" & Tid
      End If

      sTmp = StringSort(Url_Str) '把字符串按淘宝规则排序
      Sign = UCase(TaobaoAPIBasic.GenMD5(AppSevret & sTmp)) 'MD5(Secret & sTmp) '生成淘宝sign
      sURL = "http://gw.api.taobao.com/router/rest?" & "sign=" & Sign & Url_Str    '生成后的淘宝URL

      TRADES_MemoUpdate = PostURL(sURL, "")

End Function
--------------------编程问答-------------------- 拼接后的链接：http://gw.api.taobao.com/router/rest?sign=BC088B0BE2037455C73269D0CF980413×tamp=2012-08-27 23:13:14&v=2.0&app_key=21073568&method=taobao.trade.memo.update&partner_id=top-apitools&session=6102015c2203a5e7d18c7e01f415134560982vfg58919&format=xml&memo=%E6%81%B6%E6%84%8F%E6%8B%8D&tid=210968764682894

备注内容：恶意拍

补充：VB ,  控件