No. There is no update.

Word 2007 is a ten+ year-old product no longer being supported other than possibly with security updates. Word 2019 is likely to be released this year, and I doubt that the spelling checker will be significantly better than that from 2007.

Note: I considered Word 2007 to be defective when first released and have never used it for production of documents. I have and do use later and earlier versions of Word. Someone with more experience using Word 2007 may be able to give a better response as far as whether subsequent spelling checkers are improvements.

Word 2013 removed the ability to add a correction to AutoCorrect. There is a workaround for that.
Word AutoCorrect Restored