I forgot to mention that I added the following code snippet after creating the CI_COBLX fields:
ls_bapiaccountx-po_item = '00010'.
ls_bapiaccountx-serial_no = '01'.
ls_bapiaccountx-zzmarket = 'X'.
ls_bapiaccountx-zztitleid = 'X'.
ls_bapiaccountx-zzterri = 'X'.
ls_poextin-structure = 'BAPI_TE_MEPOACCOUNTINGX'.
ls_poextin-valuepart1 = ls_bapiaccountx.
insert ls_poextin into table lt_poextin.