depends on what the language pack is for.
If it is the MS MUI, then just type muisetup /? for a list of options.
To answer your question, yes you can specify which lang pack you want.
it will be something like:
muisetup /i xxxx
the xxxx is a coded number (eg. 0404 is Simplefied Chinese I think)
Hope this is what you are talking about.
Rgds,
Guav