Blanket PO

Dear All,

The difference between Blanket PO and normal PO:

1) Blanket PO = 1 time PO --> No GR --> Payment according to time horizon

2) Normal PO = Everytime PO --> GR --> Payment

My question is, can i do:

1)blanket PO = 1 time PO --> GR everytime --> Payment according to time horizon

2)blanket PO = 1 time PO --> GR (after phone call to vendor requesting goods/not based on time horizon) --> payment (after receiving goods)

Possible alternative = Contract?

Appreciate the help.