Hi Om prakash,
I did some analysis on this . The only solution for us is to debug and debuggggg standard codes.
Basically you will need below FM's to perform the above stuff.
CRM_PRIDOC_GET_HANDLE_OW -- Pass header guid and fetch ev_pd_handle value.
PRC_PD_ITEM_UPDATE --This is used to reprice the items(pass redetermine_pricing_type as B, newcalc,redetermine as X, pass pd_handle value which u got above and the item GUID).
Do a where used list of these FM's in SE37, you will get more information on how to pass values.
BR/Himayat.