How to close lots of open Purchase Orders at once?

I have a situation here, business creates Purchase Orders using a third party software and it creates open purchase orders in SAP B1, because the open purchase orders are a lot business import mass invoices using the DTW to prepare for payment. The open purchase orders and open purchase invoices do not have a link with each other, eventually the A/P Invoices are closed by a payment. The Open purchase orders remain open. What will be the best way to close the Open purchase order without using the manual procedure of closing one by one?