Someone

on *:invite:#: {
 notice `andy` You have been invited into $chan $+ , Do you want me to join?
 set %join $chan
}

on *:notice:yes:?:{
  if (%join) && ($nick == `andy`) {
join %join
msg %join YOure message thing here
  } 
}
on *:notice:no:?:{
if ($nick == `andy`) unset %join
}