code: protected void registerValueFormatter(DJGroupVariable djVariable, String variableName) {
  		if ( djVariable.getValueFormatter() == null){
  			return;
  		}
  		
  		JRDesignParameter dparam = new JRDesignParameter();
  		dparam.setName(variableName + "_vf"); //value formater suffix
  		dparam.setValueClassName(DJValueFormatter.class.getName());
  		log.debug("Registering value formatter parameter for property " + dparam.getName() );
  		try {
  			getDjd().addParameter(dparam);
  		} catch (JRException e) {
  			throw new EntitiesRegistrationException(e.getMessage(),e);
  		}
  		getDjd().getParametersWithValues().put(dparam.getName(), djVariable.getValueFormatter());		
  		
  	}
docs: Registers the parameter for the value formatter for the given variable and puts
  it's implementation in the parameters map.
  @param djVariable
  @param variableName