msflexgrid不能连接access2000？？？

Dim Conn As New ADODB.Connection
   Dim dbrec As New ADODB.Recordset
   Dim sql As String
   Conn.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & CnDg.FileName
   Conn.Open
   sql = "select * from tablename"
   dbrec.Open sql, Conn, adOpenDynamic, adLockOptimistic
   Set msflexgrid.DataSource = dbrec
最后一句错误（实时错误91：对象变量或with块变量未设置），为什么？？？