Or even better, if'you re using connect dialog to connect to servers, add your nickserv password into "password" field to each server. It'll be forwarded to NickServ upon connecing.

As for your script, you have to put that IF statement INSIDE of on NOTICE event, else it'll not work.
mIRC parser doesn't process stand-alone IF or SET statements wink

Code:
on *:NOTICE:*IDENTIFY*:*:{
  if (lagnet.org.za isin $server && $me == Seather) {
    var %passwd blahblah
    nickserv identify %passwd
  }
}