Forwarding order Manual Blocking

Dear Experts,

I am trying to do manual Blocking & Unblocking of Forwarding Order via report program.

"In case of Blocking for planning, i am passing the data as shown below:

    CREATE DATA ls_mod-data TYPE /scmtms/s_trq_root_k.

    ASSIGN ls_mod-data->* TO <ls_root>.

         <ls_root>-blk_plan =  'X'.

         <ls_root>-brc_plan =  p_brc.

        APPEND /scmtms/if_trq_c=>sc_node_attribute-root-blk_plan TO ls_mod-changed_fields.

       APPEND /scmtms/if_trq_c=>sc_node_attribute-root-brc_plan TO ls_mod-changed_fields.

     APPEND ls_mod TO lt_mod.

     go_trq_srvmgr->modify(

                            EXPORTING

                               it_modification = lt_mod

                           IMPORTING

                               eo_change       = lo_change

                               eo_message      = lo_message ).

"Finally calling Transactional Manager Save

I am successfully able to Unblock the Forwarding order which is blocked but while blocking it, i am getting an error for field Block Reason Code.

Error is "Error in Business Object Processing Framework (BOPF)"

I have also tried to update both fields separately but no success.

Am i missing something in above code? Please suggest.

Thanks in advance !!

Bhupinder