connecting cell phone to an Sony radio for auto mute function

connecting cell phone to an Sony radio for auto mute function

Hi, I have a sony radio with a att lead (mute) that i would like to connect my nokia cell phone to in order to auto mute the radio when receiving an incoming call.
I have seen the 160.00 complete nokia car kits but i was wondering if there was an easier (less expensive) way to connect the phone to the radio like via the headset plug or one wire ? off the USB data cable i already have.

thanks in advance

Frank