I can't guarantee for complete accuracy but try this:

Code:
on *:QUIT: {
  if (!$3) && ($wildtok($1-,*.*.*,0,32) == 2) {
    set $+(%,netsplit.,$network) $addtok($($+(%,netsplit.,$network),2),$nick,32)
    if ($numtok($($+(%,netsplit.,$network),32) == 1) {
      amsg There is a netsplit detected between $1 and $2
    }
  }
}
on *:JOIN:#: {
  if ($istok($+(%,netsplit.,$network),$nick,32)) {
    unset $+(%,netsplit.,$network) $remtok($($+(%,netsplit.,$network),2),$nick,1,32)
    amsg There is no longer a netsplit.
  }
}