gistfile1.php

    //Determine how the price will be calculated
    $pricingSetConfiguration->addPricingExecutionStep(
      new SetPricingElementFromContainerValue(
            array('container' => 'net_value', 
                  'pricing_element' => 'net_value')));
   
    $pricingSetConfiguration->addPricingExecutionStep(
      new SetValue(
            array('container' => 'packaging_cost_factor', 
                  'value' => '0.05')));
   
   
   $pricingSetConfiguration->addPricingExecutionStep(
      new ContainerCompute(
            array('expression' => 'net_value * 100 / packaging_cost_factor'),
            array('target', 'packaging_cost')));