Localization: Best practice suggestions Apps with mixed UI and Content languages?

I am trying to write a simple Universal app that can be easily localized to different UI languages. But the app also needs to display content that is determined by user settings. For example I would like the app UI to display in the users region (English, Russian, etc.) while at the same time having fields on the page whose strings are coming from other resources (Latin "la"? , Spanish, etc.).

The samples are pretty good about how to setup resources with respect to the UI ( e.g. Strings/en-us/Resources.resw ) but not what to do if you want to also be able to draw strings from a different language. When the words in the content fields show in Latin I don't want the UI to also be in Latin.

Suggestions on best way to do this?

Thanks,

-Tom19