Hello Yaacov,
I also faced similar problem. I do agree that RKE_FILL_BDC_CRITERIA does get called in function module POSTING_INTERFACE_CLEARING only if we fill RKE_ fields. You need to pass them in FTPOST parameter in POSTING_INTERFACE_CLEARING function module.
I wanted to pass Customer group 5 in Profitability segment. So after populating respective fields in FTPOST I added customer group 5 as shown below.
* Define Makro
DEFINE ftpost_field.
ls_ftpost-fnam = &1.
ls_ftpost-fval = &2.
APPEND ls_ftpost TO rt_ftpost.
END-OF-DEFINITION.
ftpost_field 'BSEG-RKE_BUKRS' mv_company_code.
ftpost_field 'BSEG-RKE_KVGR5' mv_misc_diff_account_cg5.
This resulted in filling of COPA segment with customer group 5 and document was posted successfully.
Thanks & Regards,
Jaideep Sharma