I'd think this is such a bread and butter kind of thing that HR has to do that someone has already written an application that does this. And since they can sell it to lots and lots of companies, they can sell it for a fraction of what you can build it for. I think that's what people here are getting at. You probably could write the code for it, but is it worth your time (and their money) for you do to it when they can just buy it - already tested and already working?