Document.ActiveWritingStyle (Word)

Returns or sets the writing style for a specified language in the specified document.

The WritingStyleList property returns an array of the names of the available writing styles.

ActiveWritingStyle (LanguageID)

LanguageID: The language to set the writing style for in the specified document. Can be either a string or one of the following WdLanguageID constants. Some of the WdLanguageID constants may not be available to you, depending on the language support (U.S. English, for example) that you have selected or installed.

With ActiveDocument 
 .ActiveWritingStyle(wdFrench) = "Commercial" 
 .ActiveWritingStyle(wdGerman) = "Technisch/Wiss" 
 .ActiveWritingStyle(wdEnglishUS) = "Technical" 
End With