I have a DirectTV Plus Receiver Model R15-100 that I need to program to control a JVC TH-M603 DVD home theatre system. I tried all of the codes provided in the Direct TV remote users guide. Code 21863 will allow the remote to turn the JVC DVD home theatre off and on but it will not operate the volume. I am using the remotes AV1 position. Does anyone know how to get the Direct TV remote to control the volume on the JVC DVD home theatre?