Lego Mindstorms to operate large motors

Hi,
I'm new to the forum and a noob regarding electronics (especially with using relays), but got a pretty comprehensive backround in RC cars etc. I've got a Lego Mindstorms 2.0 RCX (programable controller) which I want to use to operate 2 larger RC car motors. The Lego controller (RCX) has an output voltage of about 7V, but it doesn't have much current, so it can't operate 540 size RC car motors. The RCX can operate 2 small motors simultaneously in both forward and reverse directions.

I want to know, what sort of relay and circuit could I use so a powerful 7.2V high current RC battery could power the 540 size motors but still be controlled by the Lego controller? I want the motors to be controlled indepently and able to function in both forward and reverse directions.

Any help is greatly appreciated.

Thanks,
Richard

Any 12 volt relay should trigger at 7.2v.
Usually relays only take around 100ma.

Thanks for the reply smeezekitty. Do you have any idea what type of relay(s) to use and how to wire them up to work how I want?

Cheers, springninja