Arduino + Processing + SRF02 Ultrasonic Sensor + MP3

I am totally new at this and dont really have every part of the code fully understood.
I understand that inString needs a new value to stop the song from playing but i have no idea what to write. I have been searching for rewind() in the minim-library but cant really get it working.

the data for inString comes from Arduino. the float receives its value from a range sensor.

let me know if im unclear about anything else.