alias mute { 
  var %x = 1 
  while ($nick($active, %x)) { 
    mode # +vvv $nick($active, %x) | inc %x 1 
  }
  mode # +m
  mode # -havoqe $str($1- $chr(32),6)
  say $1 $+ , you are now muted from $chan until further notice.
}

That should work. It will voice everyone else first and then set +m.