reversing 12vdc polarity?

I found this site a couple of days ago and have found a wealth of info...thanks to all of you who take the time to post answers to great questions.  Just figured out how to join and need some help. 

Can someone show me how to configure a relay or IC circuit that will allow me to press a SPDT momemtary rocker switch (integrated into the steering wheel) in one direction to apply voltage to an ALPS motorized volume control?  When I press the button in the up postion i want the motor to rotate clockwise and when depressed in the other direction make the motor rotate in a counterclockwise direction?   Right now....I am thinking that the black (common) wire at the switch is always going to carry - voltage and the + voltage is always going to be either the red or the yellow wires (the switch has three wires black (grnd), red (one side of the rocker) and yellow the other side of the rocker). Unfortunately in order for this to work I need to be able to flip the black wire from - to + whenever the switch gets depressed in one of the two mechanical positions.

Ok!  Thanks for your responses!

Since this a.m. I have done some research and come up with the following schematic.  I am not the best artist but maybe someone out there can take a look at this and tell me whether it will work.  Thanks Chris

Nope, ain't gonna work, you've got a direct short on 30 on second relay.  If the left relay is relay "A" and the other is relay "B," wire like this:

relay A : 85 switched +, 86 ground, 87 constant +, 30+ to motor + terminal

Relay B : 85 switched + AND to negative motor terminal, 86 & 87 ground, 30 neg out to positive motor terminal, 87a neg out to neg motor terminal (this gives the motor a ground when this relay isn't in use, otherwise when activated we're reversing the polarity to the motor to reverse it's motion).

That should do it, or blow up your car.  Either way, problem solved.

Thanks boulderguy:

I appreciate your taking time to look at my drawing....and now that you point it out, I see my short.  The motor is a very small 50K motor that is attached to a potentiometer so I don't think anything will get burnt fried or otherwise damaged.  The switch is an integrated switch that comes from a german car....and of course there is no drop in replacement for that could function as a DPDT switch.  So....I am stuck trying to do the relay thing.  I'll give this a try tomorrow and let you know how it works...or doesn't.

Thanks again

Chris