Making Customer PO Number field mandatory when converting a Sales Quotation to a Customer Order - Apps10

Does anyone know of any way to make the Customer PO Number field (CUSTOMER_PO_NO) mandatory when converting a Sales Quotation to a Customer Order in Apps10? The relevant field on the Create Order from Quotation pop up cannot be made mandatory but our customer requires this to be completed at all times as this is good business practice. If the field is set to mandatory on the Customer Order, when using the Quote to Order process, even creating the CO in a Planned status does not force the Customer PO Number to be entered on release.