Code:
alias -l messagestyle { 
  if ($1 == text) { return $+(<,$chr(3),$cnick($nick).colour,$iif($chan && $left($nick($chan,$nick).pnick,1) isin $prefix,$v1),$nick,$chr(3),$colour(normal text),>) }
  elseif ($1 == action) { return * $nick }
  elseif ($1 == notice) { return $+(-,$chr(3),$cnick($nick).colour,$iif($chan && $left($nick($chan,$nick).pnick,1) isin $prefix,$v1),$nick,$chr(3),$colour(notice text),-) }
}
alias singlechannel { window $iif($window(@singlechannel),-a) @singlechannel }

on *:text:*:#:{
  if ($window(@singlechannel)) { echo -bcfilmrt "normal text" @singlechannel $chan -> $messagestyle($event) $1- }
}
on *:action:*:#:{
  if ($window(@singlechannel)) { echo -bcfilmrt "action text" @singlechannel $chan -> $messagestyle($event) $1- }
}
on *:notice:*:#:{
  if ($window(@singlechannel)) { echo -bcfilmrt "notice text" @singlechannel $chan -> $messagestyle($event) $1- }
}


Just type /singlechannel