请问这段代码错在哪儿了？

HTML code

<%'date signtime = formatdatetime(now,2)'response.Write(signtime)'Year(now())'Month(now())'day(now())set conn=server.CreateObject("adodb.connection")DBPath = Server.MapPath("/signin/20120720.mdb")conn.open "provider=microsoft.jet.oledb.4.0; data source="&DBpathset rs=conn.execute ("select time as st from sign where username = '"&username&"'")str =""if rs.eof thenset rs=conn.execute ("insert into sign (username) Values ('"&username&"')")If DateDiff("h",CDate(st),st) > 24 then '这里我还不知道怎么比较%>        <script language="JavaScript">          alert("今日已经签到！")          history.go(-1)        </script><%elsesql = "update sign set times = times + 1 and time =  '"&Year(now())-Month(now())-day(now())&"' where username = "&username&"'"conn.execute (sql)%>        <script language="JavaScript">          alert("签到成功！")          history.go(datecheck.asp)        </script><%end ifend if%>

代码的想法很简单，就是点击按钮签到一次，username已经获取了，在一个mdb中记录，24小时内签到一次，麻烦大神帮我改改~

[解决办法]

VBScript code

<%username = "xxxx"Set conn = CreateObject("adodb.connection")DBPath = Server.MapPath("/signin/20120720.mdb")conn.open "provider=microsoft.jet.oledb.4.0; data source="& DBPathsql = "SELECT [username], [time], [times] FROM [sign] WHERE [username] = '" & Replace(username, "'", "''") & "'"Set rs = CreateObject("ADODB.Recordset")rs.CursorLocation = 3rs.Open sql, conn, 1, 3If rs.EOF And rs.BOF Then    rs.AddNew    rs("username").Value = username    rs("time").Value = Now()    rs("times").Value = 1    rs.Update    b = TrueElse    If DateDiff("h", CDate(rs("time").Value), Now()) < 24 Then        b = False    Else        b = True        rs("time").Value = Now()        rs("times").Value = rs("times").Value + 1        rs.Update    End IfEnd Ifrs.CloseSet rs = Nothingconn.CloseSet conn = NothingIf b Then%>        <script language="JavaScript">          alert("签到成功！")          history.go(datecheck.asp)        </script><% Else %>        <script language="JavaScript">          alert("今日已经签到！")          history.go(-1)        </script><% End if %>