So you would need a script/program that interfaced with a registrar's registration system.
Since most registrar's already have agreements/contracts with someone else, they are unlikely to make it easy for you.
The incredible majority of names that get dropped that are of any value at all get picked up before most whois features get updated to let normal people know it's available. You have to have registrar access to be able to spot the drop. Good names get grabbed within seconds, and usually there are hundreds of people who have been doing this for years fighting to be the ones to get it within those few seconds.
Now, if the name is so lackluster that all the big guys *and* the people using major dropcatch services all decide they don't want it (or don't want to pay dropcatch prices, which in some cases are only $9 or so but can go, much, much, MUCH higher), then you might be able to pick it up yourself, using a script or just tying it into whois until it says available and registering it by hand.
You asking about how to get a script to run on your computer at home hoping to compete is like someone asking what they can do to fix up their house to improve their chances of being selected to host the Olympics.