How about this version?

There are still holes (office installed in irregular path, etc..), but should work for the majority.

 Code:
Function OfficeBits()
   $version = Right(ReadValue("HKCR\Word.Application\CurVer", ""), 2)
   If Len($version)
      If @OnWow64 AND Exist("C:\Program Files\Microsoft Office\Office"+$version+"\winword.exe")
         $OfficeBits = 64
      Else
         $OfficeBits = 32
      Endif
   Else
      $OfficeBits = 0
   Endif
EndFunction