Vendor valuation and document date

Hello,

we want to use vendor valuation (ME6H, ME61) in our plant.

As I know the posting date and statistical delivery date will be compared.  BUT:

Our vendor provides us the delivery ex works date. So our statistical delivery date = delivery date from vendor plant.

And thats why we cannot use posting date for vendor valuation, cause vendor valuation will be always wrong.

We want to use document date to capture vendor delivery ex works date.

Question:  can we use somehow document date for vendor valuation?

Second question: is it possible to add purchase order to vendor valuation overview (ME6H)?

Thanks in advance,

Evgenij