The absolute best way to do this is to use actual practical lighting when filming. That will always look best. Check out the behind-the-scenes video here for an example:http://fxhome.com/cinema/view/3117/coalition-of-heroes
If you can't do that, though, then a masked grade object is probably the best bet. That's what we did for this clip:http://uk.youtube.com/watch?v=IbIUXOs2Zag
Put a grade object layer over the top of your clip, apply the grading required (maybe ambient light + brightness, for example), then add a mask to limit the grading to the specific area.