I've installed my language pack, but the numbers are still in English.
A Office Language Pack only contains:
Display in Foreign language
You have to change the keyboard layout in Windows (Control Panel => Region an Language => Keyboard settings). After selecting the foreign language layout you can use it on your keyboard. If you are unable to locate the right key you can use the virtual keyboard of Windows (Start => All Programs => Accessories => Ease of Access => On-Screen-Keyboard).
You can switch between installed keyboard layouts with the shortcut ALT + SHIFT or the symbol in the taskbar.