on *:INVITE:#:{
  set %invitenick [ $+ [ $chan ] ] $nick
  notice $nick please pm me your unique code to make me join
  set %code [ $+ [ $chan ] ] $rand(231,2432)
  notice $nick your unique code is %code [ $+ [ $chan ] ] message it back to make me join
  timer 1 50 acceptedcheck #
}
on *:TEXT:*:?:{
  if ($nick == %invitenick [ $+ [ $chan ] ]) {
    if ($1- == %code [ $+ [ $chan ] ]) /notice $nick Correct code, Joining your chan now.
    set %codeaccepted [ $+ [ $chan ] ] $true
  }
}

alias acceptedcheck { 
if (%codeaccepted [ $+ [ $1 ] ]) {
join $1
unset %codeaccepted [ $+ [ $1 ] ] %code [ $+ [ $1 ] ] %invitenick [ $+ [ $1 ] ]
}
}