how to update Sales Order Delivery Block while saving Delivery ?

Hi,

I have a requirement wherein i need to update sales order delivery block field(VBAK-LIFSK) while saving the delivery for the order.

Also I need to remove this block while execution of Backorder Rescheduling program SDV03V02 (Tcode : V_V2),

Can anybody help me out in this?

regards,

Nitin