How to delete VAS packing data from sales order items ?

Hi,

   Based on some conditions 'Data in VAS packing data tab' should be deleted from lines items of the salesorder while saving, i am using 'SAVE_DOCUMENT_PREPARE' but could find the right table / process to delete VAS packing data tab info and

i have one more requirement as i need to redetermine VAS packing info based on certain conditions, is there any FM available to delete or redetermine this info? Incase if i dont find any solution, want to write BDC to delete and redetermine.  

Thanks