Plugin for replace sentences / phrases wanted

Hi!

I am looking for a plugin which will allow the user to choose a sentence and to “translate” it. There should be a database with source – destination phrases, I will fill the database with pairs of sentences.

For instance:

User find a sentence “My name is <name> and I live in <country>”
Destination text (in german): “Mein Name ist <name> und ich wohne in <country>”
It allows the user to create long letters in unknown language.
Variables as <name> and <country> should be defined for each user.

The user should be able to save and print out the letter.

Do you know any plugin?

Thank you in advance!

Amanka