What year was dd+ come out? before 2006? I think that new cable will at least give him/her surround sound at least which the receiver has.
The spec for DD +, also known as E-AC3 was first published in August 2008. I'm not sure when the first receivers started coming out with the codec installed.
Netflix stared streaming with Dolby Digital plus sometime in 2010. My pre pro is 2008 and does not have the codec. Since 2014 I understand Netflix has been withdrawing DD + support from a number of Apps, especially apps in Samsung BD players and Smart TVs, I have just found out.
So no, you can not decode a codec with a cable. However if the sending device sends 2 channel stereo, then you can get multi channels from the algorithms in the receiver such as Dolby plx, THX etc. Take your pick. It is not 5.1 however as the channels are not discrete but contrived from an algorithm that uses largely phase cues in the two channel stream.