code: public void addForwardedField(int sourceField, int destinationField) {
  		FieldSet fs;
  		if((fs = this.forwardedFields.get(sourceField)) != null) {
  			fs.add(destinationField);
  		} else {
  			fs = new FieldSet(destinationField);
  			this.forwardedFields.put(sourceField, fs);
  		}
  	}
docs: Adds, to the existing information, a field that is forwarded directly
  from the source record(s) to the destination record(s).
  
  @param sourceField the position in the source record(s)
  @param destinationField the position in the destination record(s)