Code:
alias masspm {
  ;$1 is channel, $2- is message
  var %a = 1
  var %b
  while (%a <= $nick($1,0)) {
    %b = %b $+ $nick($1,%a) $+ $chr(44)
    if ($calc(%a % 10) == 0) {
      /timer 1 $calc((%a - 10) * 3) $($+(msg,$chr(32),$left(%b,-1),$chr(32),$2-))
      %b = $null
    }
    inc %a
  }
  if (%b && %a > 10) {
    /timer 1 $calc((%a - 9) * 3) $($+(msg,$chr(32),$left(%b,-1),$chr(32),$2-))
  }
  else if (%b && %a <= 10) {
    $($+(msg,$chr(32),$left(%b,-1),$chr(32),$2-))
  }
}


using it: /masspm MESSAGE