how to attach file to send mail task

 i have xml source. my requirement is  separate null values from xml source  into  .txt file  .the .txt file saved the name with datetime like (filename=c:\src_excepption31052013140536)   i create a varible  like @[User::File_path]+@[User::File_Name]+dattetime    it is ok    when take this varible in sendmail task  the time is mismatching for seconds  then error comes like file  does not exist