Only you can decide whether it's worth the effort, and only you know the visual relationship of the two languages in the doucment … but perhaps you could roll up your sleeves and go for a two-column layout where the different languages use different styles.

.mif, which I believe most translation software is happy with, lets you wrap phrases in a language tag – but it's not really meant for humans to write. The xml lang attribute can also help. Unfortunately, I can't see any option that would save you from the chore of having to prep your text outside Word.