Delivery plant determination in sales order with a function partner

Hi,

I can't find a module function (or anything else) in order to determine delivery plant in a sales order.

What I want to do is :

1/ assign many DP function partner in the customer data with each delivery plant I could choose when I create a sales order

2/ when a sales order is created with this customer, the system asks which DP I want, and the delivery plant is updated in the DWERK or VBAP-WERK automatically ...

I imagine this is not standard but I'm not sure I'm going in the good way...

Could you help me please ?

Thanks

Alex