a300 usb remote

USB Control of Camera - Sony 300

HI

I want to take photos by pressing the enter key on my keyboard - really, just to be able to access the camera & shooting.

I really want to use it for time-lapse photography over a couple of days. Or to do other scientific sorta stuff.

How Can I do this using the USB wire or otherwise? I don't want to buy another piece of hardware, I only want a software solution. I could get an extra cord, but not another piece of hardware.

my first post on Alpha World!

Thanks for anything you know...