Something

  /set %nicklistnum $nick($chan,0)
  /set %l 1
  while (%l <= %nicklistnum) {
    if ($nick($chan, $(%l,2)) isop $chan) || ($nick($chan, $(%l,2)) ishop $chan) { inc %l }
    else { set %tovoice %tovoice $+ $chr(32) $+ $nick($chan, %l) | set %numtovoice $calc(%numtovoice + 1) | inc %l }
  }
  set %j 0
  while (%j <= %numtovoice) {
    /set %vstring %vstring $+ v
    inc %j
  }
  /mode $chan + $+ %vstring %tovoice
  /unset %j
  /unset %l
  /unset %tovoice
  /unset %numtovoice