On the similar lines as Aftab has described, if you have many price lists than better approach will be to create a custom entity where you will store the mapping and after that rather than processing the XML you will query CRM for mapping information and based on that you will filter out the results. There is a possibility that we might be able to avoid unsupported customization this way only issue is we will have to see whether we can configure the plugin to do so. Give it a shot and let's see how it goes.