Hi TM,
I haven't try but check below mentioned help. Instead of above said fields you may use XBLNR field.
The fields that can be included in a sort variant are listed, according to application, in the following structures of the Data Dictionary:
- Line item (EPOS): RFPOS and the special fields in table T021S
- Credit overview: KNKK and individual fields from RF035
- Correspondence/internal documents (KORB): RF140U
- Correspondence (KORK): RF140V
- Correspondence/line item: RF140W
- Dunning notice/dunning line item (MHND): MHND
- Dunning notice/dunning notice header (MHNK): MHNK
- Payment medium/correspondence (REGUH): REGUH and REGUSRT
- Payment medium/line item (REGUP): REGUP