SilentWolf
If the error is occurring on the line you highlighted in Red then the most obvious conclusion would be that the Table style named "Table Grid" does not exist in your document.

In English versions of Word, this would surprise me because it is a built-in style name. However, perhaps your document is not created in English and that stylename is something else in your language. You can change the code to any Table stylename that does exist in your document.

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Andrew Lockton
Chrysalis Design, Melbourne Australia