Multiple invoice number ranges

Hi all,

We sometimes have a connection problem with our branch office. During those times manual invoices are issued.Once the connections is restored SAP generated invoices are issued, and all the sales orderfor the previously issued manual invoices are entered only after office hours. The management want a different billing number range for the manually issued invoices.

Can anyone give me a detailed step of how to maintain Multiple Billing Number ranges where the Salesorder document type is the same.

for example SAP generated invoices 6500001 to 6599999

and manual invoices generated in SAP later as 7500001 to 759999