VMI part can be created in B2B portal by multiple item in one PO by Supplier

Hello, 

Now we implement VMI function, which would like to create PO by supplier, but in B2B portal, supplier only can create PO for one item in one PO each time. Are they possible to create PO by select some items into one PO each time and input different PO qty? please advise. 

Thanks

Susan