Part payment against PO related to multiple item purchased

Hi ,

Can anyone help me please,actually i have made a purchase order,that is buying different items from my supplier.

When i will make payment ,i want to make part payment againat this purchase order, that is i will pay only Rs 1300, not Rs 151425 .the unallocated amount will be RS1300.
Now how will i know which item i have paid against this purchase order and which item i have not yet paid against this purchase order.