Thanks friends, I could run CHDK on my IXUS 160 and it worked like a charm.
I just enable "remote shutter", set the "switch type" on "One Push" and "control mode" on "Normal".
Then easily connected a USB cable to camera. Whilst connecting the other end of cable to "USB port on my laptop", camera goes to "half press" mode and then by quickly unplugging the cable from "USB port on my laptop", camera goes to "full press" and picture is taken.
No DIY, No switch button, No battery, just by using a USB cable I could take pictures remotely!!! amazing!!
i would like to thank all developers and friends here who answered my questions.
I also encourage all newbies like me to start CHDK.