this will work for the nicklist (first selected nick in nicklist)... the problem for me with a channel menu is to use $$1 (= rclicked nick in that channel) and submenu: $1 or $$1 has a different funktion there confused
Code:
menu nicklist  {
  invite $snick($active,1) to....
  .$submenu($sub.invite($1,$snick($active,1)))
}

alias -l sub.invite {
  while ($chan($1) ischan) { return $v1 : invite $2 $v1  }
}