I place several large bulk orders with suppliers that we get delivered on several loads over several months. As there are several deliveries over several months, what is the best way to process the goods against the PO? As Odoo only seems to allow a complete order delivery against a PO. 

If it helps a typical example would be

1, I place a bulk PO for 10,000 tonnes of sand.

2, We call off for delivery 100 tonnes of sand per day from the supplier to be delivered.

3, I want to go into the PO and only receive 100 tonnes per day against the PO until the 10,000 tonnes on the initial order is exhausted.

Whats the best way?

Thanks