Adding spellcheck for minority language

Hi,
  I'm helping to work on a minority language that (unsurprisingly) doesn't show up in the lists of available document languages. It does have an iso639-3 (3 letter) language code, so I'm planning to use that. Does OOo accept 3 letter language codes, or is it stuck with the old 2-letter system only?

I've made (a start at) a hunspell dictionary for the language, and that works fine in the standalone hunspell spellchecker, and it shows up in firefox too, but how do I persuade OOo to allow it as a document language and thus spell check using it?

Do I need to *lie* to the program and call the language something I never expect to use (e.g. Ukranian) -- BTW, this does indeed work. Or is there a better way (without re-compiling the whole of OOo)?
The problem with lying is of course that misidentifies the text and problems loom..

I've tried unzipping the .odt file and editing the contents to set the language code to match the dictionary, but that doesn't solve the "turn on the spellchecking in Options/Language settings/proofing tools" step that I can't reach. The result of that seems to be that no dictionary is used at all.

Is there some file somewhere which contains a list of languages and their codes, or something simple like that?