Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Am sure is possible but not practical.

A DVR needs to be its separate box and stationary.

I have heard of using a Mini...
 
Elgato makes devices that allow the mac to perform as a dvr. A mini might be a better choice than a macbook.
 
I use an Elgato EyeTV HD (199.00) connected to an old Mac Mini and it works great. For fun, I hooked it up to my new rMBP and encoded some recorded video and it did it in a fraction of the time.

So yes, it's possible, check out Elgato's website to get the hardware you need to connect to your Macbook.
 
Is it possible to make use my mbpr as a dvr?
If you had a spare Mini or an old iMac, your idea would make sense. But it's a shame to use your rMBP as a DVR. Even if you could still use the laptop when it's recording, the DVR function would probably be very CPU-intensive.

I would recommend against it.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.