Task essence:

My task was to set Block ID and Text automatically while end-user created purchase requisition in ME51N.

Why do it? Because, it should be approved in another SAP module (PSM-FM) and only after this it can be converted to PO.

My solution:

First of all, look at SE11, structure MEREQ_ITEM_S_CUST_ALLOWED. There are no such fields (block id and text) there.

Create append structure.

Then, implement BADI ME_PROCESS_REQ_CUST, create 1 attribute and write code of 2 methods:

G_TRTYP Instance Attribute Private Type TRTYP

  METHOD if_ex_me_process_req_cust~open.
     me->g_trtyp= im_trtyp.
  ENDMETHOD.

  METHOD if_ex_me_process_req_cust~process_item.
    CHECK  me->g_trtyp  = 'H' . " creatingmode
    CHECK im_count= 1  .

    DATA  reqdata   TYPE mereq_item.
    CLEAR: reqdata.
    reqdata= im_item->get_data( ) .

    reqdata-blckd   = '1' .
    reqdata-blckt   = 'need to approve' .
    im_item->set_data(reqdata) .

    DATA: ls_dataxTYPE mereq_itemx.
    MOVE: 'X' TO ls_datax-blckd,
          'X' TO ls_datax-blckt.

    im_item->set_datax( ls_datax) .
ENDMETHOD.

That's all. Have a nice day