Well, you can kind of force a semi-dormancy I suppose - keep them in a cool, dim area for the winter and water them a little once a month or so. Not sure how they will do but I have treated a few begonias years ago this way in my very cool garage. I still think the better way to go is give them light, warmth, water as needed, and maybe a hard haircut. The other thing to do is treat them as annuals - just toss them and buy some more next spring.