in the autoexec.conf:
exec gamma.cfg

gamma.conf:
bind PGDN "vstr gamma_down"
bind PGUP "vstr gamma_up"
set gamma_0 "r_gamma 0.8 ; set gamma_up vstr gamma_1 ; set gamma_down vstr gamma_0 ; r_gamma ; play sound/player/gurp1.wav"
set gamma_1 "r_gamma 0.9 ; set gamma_up vstr gamma_2 ; set gamma_down vstr gamma_0 ; r_gamma ; play sound/player/gurp1.wav"
set gamma_2 "r_gamma 1.0 ; set gamma_up vstr gamma_3 ; set gamma_down vstr gamma_1 ; r_gamma ; play sound/player/gurp1.wav
set gamma_3 "r_gamma 1.1 ; set gamma_up vstr gamma_4 ; set gamma_down vstr gamma_2 ; r_gamma ; play sound/player/gurp1.wav"
set gamma_4 "r_gamma 1.2 ; set gamma_up vstr gamma_5 ; set gamma_down vstr gamma_3 ; r_gamma ; play sound/player/gurp1.wav"
set gamma_5 "r_gamma 1.3 ; set gamma_up vstr gamma_6 ; set gamma_down vstr gamma_4 ; r_gamma ; play sound/player/gurp1.wav"
set gamma_6 "r_gamma 1.4 ; set gamma_up vstr gamma_7 ; set gamma_down vstr gamma_5 ; r_gamma ; play sound/player/gurp1.wav"
set gamma_7 "r_gamma 1.5 ; set gamma_up vstr gamma_8 ; set gamma_down vstr gamma_6 ; r_gamma ; play sound/player/gurp1.wav"
set gamma_8 "r_gamma 1.6 ; set gamma_up vstr gamma_9 ; set gamma_down vstr gamma_7 ; r_gamma ; play sound/player/gurp1.wav"
set gamma_9 "r_gamma 1.7 ; set gamma_up vstr gamma_A ; set gamma_down vstr gamma_8 ; r_gamma ; play sound/player/gurp1.wav"
set gamma_A "r_gamma 1.8 ; set gamma_up vstr gamma_A ; set gamma_down vstr gamma_9 ; r_gamma ; play sound/player/gurp1.wav"
vstr gamma_4