Connecting receiver and DVD recorder to record in surround sound

Considering purchase of an Onkyo HT-S3500 home theater system. I presently own a Magnavox DVD recorder which I would like to use to record surround signal programming from my local cable TV provider. The signal path/connections would be as follows (unless you tell me different):

Incoming cable to cable box.
Cable box HDMI output to Onkyo receiver HDMI CBL/SAT input.
DVD recorder HDMI output to Onkyo receiver VCR/DVR HDMI input.
Onkyo receiver HDMI output to TV HDMI input.

The question then is how do I get the A/V signal back to the recorder in such a way that I preserve/record the surround sound audio? The recorder has a Coaxial digital audio output, but no corresponding input.

I've looked at the manuals for both the receiver and the recorder and it's just not clear as to how this is done.

I appreciate help getting me on the right path, no pun intended.