Vedhæft fil on the fly

Hej,
Jeg genererer en rft fil med følgende kode:

  // including main script file:
  include "rtf_class.php";
  // this will be the name of our RTF file:
  $navn = "filnavn";
    $file_rtf = "$navn.rtf";
  // HTTP headers saying that it is a file stream:
  Header("Content-type: application/octet-stream");
  // passing the name of the streaming file:
  Header("Content-Disposition: attachment; filename=$file_rtf");
  // here is the text of our RTF file:
  // creating class object and passing to it the path to configuration file:
  $rtf = new RTF("rtf_config.inc");
  // passing the text to the object:
  $rtf->parce_HTML($html_text);
  // getting RTF code:
  $fin = $rtf->get_rtf();
  // streaming the file to the user:
  echo $fin;

Jeg har nu brug for at vedhæfte filen en mail. Filen indlæses i denne variabel, i det script jeg normalt bruger til at sende vedhæftede filer med:

$fil_var = fread(fopen($_FILES['fileatt']['tmp_name'], "r"), filesize($_FILES['fileatt']['tmp_name']));

Men jeg ved ikke helt hvordan jeg kobler de 2 ting sammen :)