With the text-to-speech extension, you can change the language with this block:

set language to [English v] :: pen

However, if you try to do this:

set language to (variable) :: pen

which it allows you to do, it won't actually set the language, even if the variable has a value exactly the same as a language available.
So, I suggest that you can do this, as it would be much easier than having to make a super long block that says “if var = English set language to English, else if var = Spanish (European), else…”

Support

I'm surprised this isn't a thing, and it makes sense that it should work.