Once you have set the language for any text, Word continues to recognize it in other documents.
In an earlier step, you were told to select the Detect language automatically option as part of setting the language of text. This is because after you initially set the language for multilingual text, if you selected the Detect language automatically option, the text language will automatically be identified as you continue to type in the same language.
In Word 2007, once you have set the language for any text, you shouldn't need to set again for that language in other documents. Once you set the language, Word continues to recognize it as one that you use.