I would be wary about using hire-a-coder sites as I've heard some horror stories about the quality of people on them.
As above, if you can give an idea of what the program needs to do we'll be in a better position to advise.
If it's anything non-trivial though, you'd probably be better off getting a proper company to do it, but be aware that it won't come cheap.
You may be able to get someone to do it cheaply from a website, but you will get what you pay for.