Determine exchange rate type automatically in shipment

[Bea2310]

Dear all,

my client uses eWM to post the deliveries and to create the shipment.

The user goes into VT02N to manually add freight cost but once, the invoice gets created the system automatically determines the M Rate instead of the one which is assigned to the customer master.

Is there a way to automatically fill the exchange rate type in the shipment once the user enters manually the condition?

Regards
Beate