Customer Downpayment for Sales orders

Dear Gurus,

The Client receives advance payment from the export customers and enters into the system.

The advance payment is indeed a bulk payment and the Client is not able to link the individual Sales Order while creating downpayment in SAP system. Currently they are entering the Sales Order number in the Text Field during Downpayment creation.

Kindly advise any option to include the Sales Order numbers during downpayment creation in SAP.

Regards,

RK