The "beta" package is already available and can be downloaded here (v0.5, update of May, 28th, 2013), please read the README-IMPORTANT file which is located in the package. You need to select "Finnish" as input language to activate the Latin spellchecking.
Be aware that this package was designed on MacOSX 10.6. On MacOSX 10.8, 10.9 and 10.10, the Apps sandboxing feature can prevent the option dialog box from saving the spelling options. This problem is fixed in the MacOffice2016 version.
For MacOffice 2016, go to the dedicated page here.