Code:
alias massdeop {
  :begindeop
  unset %nicks
  if ($nick($$1,0,o) > 1) {
    var %i = 0
    :checkdeop
    inc %i
    set %curnick $nick($$1, $+ %i $+ ,o)
    if (%curnick != $me) { set %nicks $addtok(%nicks, $+ %curnick $+ ,32) }
    if ($numtok( $+ %nicks $+ ,32) == 3) { .mode $$1 -ooo %nicks | goto begindeop }
    else { goto checkdeop }
  }
  else { goto end }
  :end
}

Usage //massdeop #channel

This code freeze your mIRC and disconnect you for Connection Reset By Peer. shocked