Can you make your TV have 3 separate boxes with different tv channels in each?

I have a 42 inch vizio and a comcast HD box. My question is, can you make 3 boxes appear on your tv with 3 different channels in each, like a split screen? This came from the idea of having 3 Televisions with different channels, but I don’t want to buy 2 more tv’s. So, is this possible? If so, how can I do it?

It’s a feature of the TV commonly called picture in picture. Your TV would have to support it.