Beaner's got a point. But im probably on the same level as you are...Basically I sometimes have to do the same thing. I have been growing a Thai plant for about 4 months now and because the weather were i live isn't that great, I will be moving it from complete natural sunlight to an hps light indoors. Doesnt harm the plant in anyway. If anything, it gives it more of a chance.
Just make sure you have a good grow spot: out of the way and not in sight.