Hi Alexandra,
I understand it can be tricky to understand the solution as a year after it was hard for me to understand what I wrote.
So :
1st : start "regedit" or "regedit32" (windows Key + R then type regedit)
2nd : look for the subchain "Excel.application"
3rd : you can see the version installed on your workstation (for your information the 2013 office version use the number 15)
4th : add a new key "name : version of office "11" and data : "Excel.application.11" to pretend it is also installed on your workstation.
So MDM DM will look for "Excel.application.11" and would find it then will use the CLSID correponding to your real office version.
Hope it is more clear now.
Regards,
Hacene C.