If you go to the CHDK Settings -> Remote Parameters menu, did you set Enable Remote [ * ] ?
A couple of other script suggestions :
while 1
do
sleep(100)
k = get_usb_power
until k>0
if k > 35 and k < 43 then gosub "shoot"
if k < 6 then gosub "zoom100"
if k > 5 and k < 12 then gosub "zoom80"
if k > 11 and k < 18 then gosub "zoom60"
if k > 17 and k < 25 then gosub "zoom40"
if k > 24 and k < 32 then gosub "zoom20"
if k > 31 and k < 36 then gosub "zoom10"
wend
end
:zoom10
print "zoom10"; k
set_zoom 10
sleep 1000
return
:zoom20
print "zoom20"; k
set_zoom 20
sleep 1000
return
:zoom40
print "zoom40"; k
set_zoom 40
sleep 1000
return
:zoom60
print "zoom60"; k
set_zoom 60
sleep 1000
return
:zoom80
print "zoom80"; k
set_zoom 80
sleep 1000
return
:zoom100
print "zoom100"; k
set_zoom 100
sleep 1000
return
:shoot
print "shoot"; k
shoot
sleep 1500
return
Also note that set_zoom puts the zoom in a position defined the number of zoom steps. If your camera only has 7 or 8 zoom steps then every one of the functions listed above will move the camera to the 100% position.