Help with Vu Meter in Kontakt

[claud9]

Hello,
I have set up a custom made Vu Meter that respond to velocity in Kontakt.
My instrument has four groups and each group assigned to Bus 1 to 4.
Actually the Vu Meter respond to all groups together.
I would like to assign the Vu Meter to respond to a specific Bus.
My intention is to create 4 different Vu Meters and each respond to one of the four Buses.

I copy the code below, what line of code I have to add to assign this meter to a specific Bus (Bus1 for example)?

on init
set_ui_height_px(250)
make_perfview
declare $fg4rw
declare ui_slider $ywzts(0, 127)
set_control_par_str(get_ui_id($ywzts) ,$CONTROL_PAR_PICTURE, "vu_meter")
end on
on note
$ywzts := $EVENT_VELOCITY
end on
on release
if (search (%KEY_DOWN, 1) = -1)
while ($ywzts>0)
$ywzts := $ywzts-1
inc($fg4rw)
wait(9000)
end while
end if
end on

Any help is welcome

Thanks!