On my Samsung TV there is an auxiliary control system called Anynet that provides automatic operation of an external device (and vice versa). In my case, I have a Samsung upscaling DVD player that does what you want to do with your Sony. I just turn on the DVD player, insert a DVD, and the Anynet system turns on the TV and switches its input to the DVD player. It works great.
The kicker is, the DVD player has to be Anynet-equipped, and yours probably isn't. In fact, it may need to be a Samsung device to have Anynet.
My Samsung is 2 years old, so maybe there's some other provision on newer sets. If not, then it would seem that what you would like to do isn't going to happen.
