Solution : https://service.sap.com/sap/support/notes/1440212 (SAP Service marketplace login required)
Key words : 
prerequisites programm error solution sap netweaver bw 7, sap netweaver bw 7, duplicated 'n' times, sap nw bw7, function module rsah_launch_excel, 01 bi abap sp07, 02 bi abap sp04, check sap note 875986, 'n' distinct variables, 00import support package 24
Related Notes : 
       
| 1440497 | RRMX:Variables are ignored while executing RSAH_LAUNCH_EXCEL | 
| 1431124 | SAPBWNews NW BW 7.02 ABAP SP04 | 
| 1419541 | Preliminary version SAPBWNews NW BW 7.10 ABAP SP10 | 
| 1407599 | Preliminary Version SAPBWNews NW BW 7.20 ABAP SP03 | 
| 1407598 | SAPBWNews NW BW 7.0 ABAP SP 24 | 
| 1401477 | SAPBWNews NW 7.x BW Add-On Frontend Patch 1200 - GUI 7.10 | 
| 1392433 | SAPBINews NW7.11 BW ABAP Support Package 05 | 
| 1369294 | SAPBINews NW7.01 BW ABAP Support Package 07 |