[MS Office 2007 Pro Plus] Silent installation of additional MUI

Hi

I am struggling with installation of additional MUI on an existing
installation of MS Office 2007. I have installed using .msp and the following
..xml file:

Configuration Product="ProPlus"

Display Level="Basic" CompletionNotice="no" SuppressModal="no"
AcceptEula="Yes" /

AddLanguage Id="en-us" ShellTransform="Yes" /

Setting Id="Reboot" Value="Never" /

/Configuration

Installation is successfull - I have MS Office 2007 with English MUI. Now I
would like to add additional MUI. I am trying to do it with the following
command:

\\%path%\setup.exe /modify ProPlus /config \\%path%\config.xml

Here you can see xml file:

Configuration Product="ProPlus"

Display Level="Basic" CompletionNotice="no" SuppressModal="no"
AcceptEula="Yes" /

AddLanguage Id="en-us" ShellTransform="Yes" /

AddLanguage Id="pl-pl" /

Setting Id="Reboot" Value="Never" /

/Configuration

After this command I still have only English MUI. I have tried to install
both English and Polish MUI during the first installation of MS Office 2007 -
then it works fine. I have also tried to remove one MUI (using the
RemoveLanguage command in xml) and it also works fine. But the problem is
when I am trying to add MUI to an existing installation of MS Office 2007.

Any help would be appreciated

Thanks in advance
Tomasz