Can I link my POS to my security DVR?

I have a small business. I have been planning to put in a CCTV security camera system that records on a DVR. I also plan to put in a new Point of Sale system with touch screen registers. My question is can I split off the feed to my register screens and somehow send it to the security DVR on one of the channels so that I not only have a recording of the transaction on the camera feed, but a recording of the actual transaction on the register screen as it happened on one of the other DVR channels thus linking the two events through the DVR.

So my question is can I make the feed for the register screen one of the channels I am recording on the DVR? Anyone know how to do this? I am a complete novice.