Code:
on *:JOIN:*:.timer 1 1 maxjoin $chan
alias maxjoin {
  echo -a JOIN $1 $nick($1,0,a) $($+(%,chanmax.,$1),2)
  if ($nick($1,0) < $($+(%,chanmax.,$1),2)) { return }
  set $+(%,chanmax.,$1) $v1
  ;;;; Your actions below this line ;;;;
  describe #chat18+ The New record High user count for #chat18+ is: $v1
}

on *:TEXT:!count:#:{
  if ($($+(%,chanmax.,$chan),2) !isnum 1-) return
  ;;;; Your actions below this line ;;;;
  describe $chan Current Record high user count for $chan is: $v1
}