auto-fill field “Ship to”- rules

Hello,

Do you anybody know according to which rules is automatically filled field “Ship to” after filling in field  “Customer” in  form “Repair Orders”

 Example :
the customer has the following (ship to) sites :
1) address 1
2) address 2
3) address 3
4) address 4 – is designated as the primary in business purpose tab in customer setting (see picture)

 

After filling in field “Customer” in form “Repair Orders” system automatically insert ”Address1” to field “Ship to” instead “address 4” (primary)

 

Thank you

Petr