Merge Multiple Posted Sales Invoice in to one document

Good Morning, 

We are currently using NAV2009 and are in the process of upgrading to Dynamics Business Central.  We have multiple customers who require a single invoice for all purchase orders.  Often items ship separately, which creates multiple invoices for their single PO.  Is there a way to Merge Multiple Posted Sales Invoices in to a single document? 

Thank you, TrishSafariMicro