Solution : https://service.sap.com/sap/support/notes/534193 (SAP Service marketplace login required)
Key words : 
system field sy-tcode, maintenance/service order confirmation, active transaction variant exists, standard transaction cn25/iw41, transaction sy-tcode, function module rs_hdsys_get_tc_variant, active transaction variant, terms cn25, standard transaction, transaction variant
Related Notes : 
       
| 1081448 | Confirmation using variant transaction | 
| 601129 | |
| 600546 |