Code:
If EXIST(%%ProgramFiles(x86)%%)
  ;Windows = 64-bit, check for Office
  If EXIST("%%ProgramFiles%%\Microsoft Office\Office15\WinWord.exe")
    ? "Office 64bit")
  EndIf
  If EXIST("%%ProgramFiles(x86)%%\Microsoft Office\Office15\WinWord.exe")
    ? "Office 32bit"
  EndIf
Else
  ;Windows = 32-bit, if there is office, office will be 32-bit
EndIf