Hi Murali, the solution is when you fill the data in the structure cha_shipments_at_save-new_vbpa[].
Make sure to fill the field UPDKZ with an 'I' or 'U' before appending the information.
"insert or update flag
w_vbpa-mandt = sy-mandt. " Client
w_vbpa-vbeln = fp_w_vttk-tknum. " Shipment
w_vbpa-parvw = l_c_char_sp. " Partner
w_vbpa-lifnr = fp_w_vttk-tdlnr. " Fordwaring Agent (in my case)
w_vbpa-updkz = l_c_i. " Insert entry in table.
APPEND w_vbpa TO cha_shipments_at_save-new_vbpa[].
Best regards.
Nicolas.