Function b(filename As String, sheetname As String) As Boolean
    Dim rst    As DAO.Recordset
    On Error Resume Next
    Set rst = CurrentDb.OpenRecordset("Select *  FROM [excel 8.0;database=" & filename & "].[" & sheetname & "$]")
    'b = (Err.Description <> "'" & sheetname & "$' 不是一个有效名称。请确认它不包含无效的字符或标点，且名称不太长。")
    b = (Err = 0)
    rst.Close
    Set rst = Nothing
End Function