Update of shipping condition in a sales order

Hi All!

I have a sales order where the sold-to-party and the ship-to-party are the same (from the customer master data). At header level, in the shipment condition field of the Shipping tab, I have the value from the Sold-to-party master data. If i chose a different Sold-to-party partner, I want that the value of the shipment condition to be updated automatically by the system (from the Ship-to-party master data). The system only issues the message:

"Check route for Ship-to party 0000025237 in document header. (Message no. VPD 008)".

Can I do it from Customizing or should I use a user exit for this?

Thanks for your help.

Florina C.