New shift kit idea - Anyone who knows a little about electronics?

[TwistedEL]

I have been thinking of doing this for a while and now I am starting to plan for it.

The stereo controls on my steering wheel are next to useless with the aftermarket head unit, and I have learned to live without them. I'm planning on using the buttons for something else. I want to make a 4 stage shift kit and utilise the "Mode" button on the wheel to control it.

However I have never attempted anything quite so complicated (even though in the scheme of things it is in fact not very complicated) so I would like just a little help designing the circuit. I have done up a draft diagram and I'm hoping someone can take a look at it and tell me where I have gone wrong (and most likely I have!) and give some input.

The diagram is attached. I have left most of the resistor values blank, because I really have no idea what they should be...

The way it will (or is intended to) work is: You turn on the car. Everything is as it should be (the kit is off or in mode 0). You press the mode button to go to stage 1 and press again for 2 and 3. Each mode increases in firmness. Pressing again while in mode 3 will turn the kit back to 0.

Can anyone help me?