Autofill of route field in VL01 screen based on incoterms field.

Hi Experts,

I got a requirement of filling with dummy route based on incoterm condition. I can validate it at the time of saving using user exit.

But requirement is to get filled in the related screen 1108 of field Route as dummy route based on incoterms.

How can we achieve this or else only possibility is to write validation while saving.

Regards/Anand