At the moment you're simply reading whether the button is down to start the replay sequence:
fPlayMode = digitalRead (DigitalInStartStop);
What you're trying to do needs you to detect when the button state changes from unpressed to pressed; each time that happens, toggle the state of fPlayMode. To detect button state changes you need to remember the previous state and see whether the current state is different; afterwards, save the current state as the new previous state ready for next time.