1) This should've been posted in the Scripts and Pop-Ups section, especially since you knew it was going to be a script, per your subject line.
2) This script presumes that you use the same password for all of your nicks and that the nick registration service is called nickserv.
on ^*:notice:*is registered*:*:{
if ($me isin $1-) && ($nick == nickserv) {
.msg nickserv identify <password>
}
}
on ^*:notice:*You are now identified*:*:{
if ($nick == nickserv) {
.msg chanserv invite <#channel>
}
}
You may need to edit these for the actual messages, as well as the network and channel names.