List of Bills created based on the Po No field

Hi,

In the copy control between Delivery and Invoice.

I have seen two fields

1)Assignment Number

2)Reference number

Our requirement is we need to find the list of invoice created based on the  PO number field(VBKD-BSTKD),while creating sales order,user will key in PO No.We do partial delivery and invoices.We need to find list of invoice created when we key in Po No,is there any standard report available,based on this criteria.I believe if we maintain Po number as Assignment Number/Reference number in copy control.

Thanks,

Pradeep M