There are really two questions here:
1. Does your TV have a "variable" audio output? (If it does it would only be through the stereo L/R RCA jacks.) In this case, when you set the remote for the 211 to control the Sony TV, it will automatically be set to control the TV volume, or more specifically the variable audio output to the A/V receiver. Note that the best you can do with this setup is Dolby Pro Logic sound.
2. How many inputs (211, DVD, VCR, ect.) do you have going to your plasma? If it's only one (the 211), it might be better to take the optical digital from the 211 direct to your A/V receiver (if it has a digital input), and just set the 211's remote to control the A/V receiver's volume whenever in SAT or TV mode. There is a procedure for this in the manual. You MAY want to do this even if you have several source components going into the TV, BUT beware that some TVs only pass through stereo sound to the digital audio output from outside HDMI or digital source inputs (my Panny is that way).
Hope this helps.
Brad