alias bextract {
  var %be.1 = $gettok($2,1,59)
  var %be.2 = $gettok($2,2,59)

  var %start = $bfind($1, $iif($3, $3, 1), %be.1)

  if ($prop == no) var %start = $calc(%start + $len(%be.1))

  var %end = $calc($bfind($1, %start, %be.2) - 1)

  if (($calc(%end - %start) > 255) || ($calc(%end - %start) < 1)) return $null

  var %return = $bvar($1, %start $+ - $+ %end).text

  if (%return isnum) return $null
  else return %return
}