hmm. depending on what model of machine, you could use the normally open side of the carrier switch to light the "correct-change" lamp ,
if it's a cavalier with a "Have a Coke" light, you could just wire it in parallel,
or if it's a vendo, (as stated above) run a wire up from the normally open side of the carrier switch at the bottom of the bottlerack, but you'd have to isolate the "correct-change" lamp from the original harness wires,
or you could make a smal self-latching relay triggered by the "free-play" switch. but all options involve some rewiring of the machine.
easy for me. harder for you, unless you are electrically inclined.
do be carefull though, you are dealing with line voltage.
