settlement rule_PP

Dear friends,

My strategy is make to stock production. I have run MRP in MD02. Through MRP i have created my production order. So system automatically created settlement rule for my order as " Category :MAT (Material) and settlement type as "FUL". (Full settlement) . These two fields are frozen by default and i can not change. Is it possible to change the settlelement type as PER (periodic settlement) instead of "FUL" for category "MAT".

Please guide me

Thanks

Senthil