This should work.

Code:
on 1:OPEN:?:*:{
  var %nick = $replace($nick,$chr(124),$chr(95),$chr(92),$chr(95))
  var %ctime = $calc($ctime - $file($+($logdir,%nick,.,$network,.log)).ctime)
  echo -a $iif(%ctime < 5,Log created for $nick,Log exists for $nick)
}