ok, I have managed it after all  

In the section:
function onClose() {
var abc = defineWorkPlane(currentSection, true);
  writeBlock(
    gMotionModal.format(0),
    conditional(machineConfiguration.isMachineCoordinate(0), "A" + abcFormat.format(abc.x)),
    conditional(machineConfiguration.isMachineCoordinate(1), "B" + abcFormat.format(abc.y)),
    conditional(machineConfiguration.isMachineCoordinate(2), "C" + abcFormat.format(abc.z))
  );  
Maybe someone else can use it  

Greetings
Olli