SSAS 2012 end Excel functions - mode.sngl doesn't work

Since I've used SSAS 2005 with Excel 2007 my Excel.Mode function worked fine.

Now we have migrated to SQL 2012 and we have installed Excel 2010 --> Excel.Mode is deprecated in the new version and the cube calculations that use this function won't work. The new Excel way to calculate mode is [mode.sngl] but I can't call it from cube calculations.

I tried to replace the Excel approach with the MDX approach (link below) but the time to calculate is too slow.

http://social.msdn.microsoft.com/forums/en-us/sqlanalysisservices/thread/C70DE994-5815-4B30-A10A-81518F784BD2

Can anyone suggest me how to procede?

Thank you in advance