Add steering audio control to Honda?

I have an '02 Civic with a stock cd/radio. It has one knob for pwr/vol control. I am planning on making an external pwr/vol controler to fit inbetween the spokes on the left side of the steering wheel. I am planning on interrupting the circuit w/in the head unit, running wires through the steering column, and attach to two devices. One device will control pwr, the other will be a soft switch to control vol+ and vol-.
I searched for a prefab unit to retrofit to stock stereos, but seems like none are around. Anyone have any input on the device I will attempt to make, or input on the search for a retro kit?
Thanks to all.

Sorry I don't know if I understood exactly what you said--Are you using an aftermarket radio or just the stock setup?

I am sorry for the confusion.
I have a stock cd/stereo in my civic. I want to keep this stereo in the car. I want to add my own custom power and volume controls between the spokes in the steering wheel. Kind of like the factory cruise control in a lot of cars, only I want to be able to control the radio functions. I figure I can build a simple circuit with resistors or pots for the volume control, and a soft-switch for the power. However, if I just add the additional controls on the steering wheel, I am wondering if I will have to utilize the ones on the stereo as the master controls and the new controls as secondary.
Clear as muddy water?