I have modified the purchase order field so that staff can use it to process check or cash payments. The PO number is being used as a passcode field...which only staff know. This works! A regular visitor can't submit the cart if they don't know the code. But I would like to add an additional custom field to the PO section that only shows when the PO option is selected and this field would contain the Check number. I know you can add custom fields, but how do you add the custom field to the Purchase Order section? And equally important, what is the way to access this custom PO field data from the XML datafeed? (if it is the same as other custom fields, no problem).