I would suggest to not copy the standard
- Extend RFPOS[X], execute RFPOSXEXTEND, use BAdI FI_ITEMS_CH_DATA to add the new displayed fields in standard transaction too (read the links I provided)
Then either
- You can add selection with Customizing or tables of logical database DDF (kna1, knb1, bs[i,a]d, etc.) do it
- Else create a small wrapper using same logical database than FBL5n/RFITEMAR with your own selection field with extra criteria, and call FM FI_COMPANY_CODE_DATA, ITEM_DERIVE_FIELDS to enrich data and last FI_ITEMS_DISPLAY to display with caller_repid = 'RFITEMAR' and acctype = 'R', you will share ALV variant with FBL5n but there should not problem, as you have the same data to display.
Which fields did you add in selection, from which table ?
Regards,
Raymond