Hi Ashwin,
You can maintain three valuation class in Material Master Accounting Screen.
1 . Valuation Class - Which has to be mentioned in OMSK.
2. Sales order val.class
3. Project stock Valuation class.
According to your case:
1. Valuation class : Domestic
2. Project stock valuation class: Import
You can maintain project stock valuation class in wbs.
Regards,
Vivek