a little bit cleaner version :

Code

on !*:JOIN:#:{
  if ($nick($chan,$me,~&@%)) { 
    if ($+(%,JoinPartFlood_,$site,_,$chan) == $null ) { set -u10 $+(%,JoinPartFlood_,$site,_,$chan) 1   }
    else { inc $+(%,JoinPartFlood_,$site,_,$chan)  }
    if ($($+(%,JoinPartFlood_,$site,_,$chan),2) == 3) {
      if ($wildsite !isban $chan) { mode $chan +b $wildsite }
      if ($nick ison $chan) { kick $chan $nick Join-Part-Flood }
      unset $+(%,JoinPartFlood_,$site,_,$chan)
    }
  }
}