I couldn't get the vars to set right but I'm pretty sure this would work.

on *:invite:*: {
  if ($nick ison #YOURCHANHERE) { 
    join $chan
    ;Number of channels they've invited you to
    inc %chans. $+ $address($nick,2)
    ;This should look like %chan.*!*@Blitzjager.users.quakenet.org.#OfChans #Blitzjager #Blitzjager2
    set %chan. $+ $address($nick,2) $+ %chans. $+ $address($nick,2) $addtok(chan. $+ $address($nick,2) $+ %chans. $+ $address($nick,2),$chan,32)
  }
  else /notice $nick Please Idle in #YOURCHANHERE before you invite me to your #
}
on *:part:#YOURCHANHERE:{
  while ( %chans. $+ $address($nick,2) > 0) {
    part $gettok(%chan. $+ $address($nick,2) $+ %chans. $+ $address($nick,2),%chans. $+ $address($nick,2),32)
    dec %chans. $+ $address($nick,2)
  }
  unset %chan. $+ $address($nick,2) $+ %chans. $+ $address($nick,2) $addtok(chan. $+ $address($nick,2)
}