Need help using setDefautl() of XLocale Interface

[Herr Proffessor]

Hi, i'm trying to change the default language of Open Office from a macro. I think i can do this using the setDefault() method of the XLocale interface. The problem is that i don/t know how to use it because the interface is not part of a service. It depends directly from the resource module. I don't know if i have to create a service or not, and if i have to, which one.
I tried just using it, but did not work.

Thanks a lot