Code:
[color:green]; define the max. number of bans in the list[/color]
alias maxbans { return [color:blue]100[/color] }
[color:green]; define the max. number of bans allowed left in the list when clearing[/color]
alias bansallwd { return [color:blue]75[/color] }
   
[color:green]; you could use the on ban event to check everytime a ban gets added[/color]
on *:BAN:[color:blue]#channel[/color]: {
  [color:green]; if the banlist holds 5 open slots or less[/color]
  if ($ibl(#,0) >= $calc($maxbans - [color:blue]5[/color])) clearlist $chan
}
   
[color:green]; or you could use a timer that checks (in this case) every 5 minutes[/color]
on *:CONNECT: {
  [color:green]; if the banlist holds 5 open slots or less[/color]
  .timerclrclst -o 0 [color:blue]300[/color] if ($!ibl([color:blue]#channel[/color],0) >= $calc($maxbans - [color:blue]5[/color])) clearlist [color:blue]#channel[/color]
}
   
[color:green]; clear the list[/color]
alias clearlist {
  [color:green]; error checking[/color]
  if ($1 !ischan) echo -a [color:red]Error in function call to function clearlist - specified argument is not a valid channelname[/color]
  else {
    [color:green]; set start of loop (end = $bansallwd)[/color]
    var %x = $ibl($1,0)
    [color:green]; we're gonna be needing this variable later on - it should not exist, but just to be safe...[/color]
    unset %b.tmp
    while (%x > $bansallwd) {
      [color:green]; to prevent a unban flood we're gonna group the unbans in groups of 5[/color]
      %b.tmp = $addtok(%b.tmp,$ibl($1,%x),32)
      [color:green]; unban when the group hits 5[/color]
      if ($numtok(%b.tmp,32) == 5) .mode $1 -bbbbb %b.tmp
      [color:green]; clear the variable for the next load[/color]
      unset %b.tmp
    }
    [color:green]; if the bans to be removed isn't a multiple of 5, there will be bans left to undo[/color]
    if (%b.tmp) .mode $1 $+(-,$str(b,$numtok(%b.tmp,32))) %b.tmp
    [color:green]; always clean up your mess[/color]
    unset %b.tmp
  }
}


You need to change the parts in blue to your custom values, the rest should pretty much work without changing it. Of course theon connect event and the on ban event don't need to be used both - pick one.

DALnet #Helpdesk
I hear and I forget. I see and I remember. I do and I understand. -Confucius