Document.StyleSortMethod (Word)

Returns or sets a WdStyleSort constant that represents the sort method to use when sorting styles in the Styles task pane. Possible return values are wdStyleSortByBasedOn - Sorts styles based on the item indicated in the Sort Styles Based On option, wdStyleSortByFont - Sorts styles based on the name of the font used, wdStyleSortByName - Sorts styles alphabetically based on the name of the style, wdStyleSortByType - Sorts styles based on whether the style is a paragraph style or character style, wdStyleSortRecommended - Sorts styles based on whether they are recommended for use.

ActiveDocument.StyleSortMethod = wdStyleSortByBasedOn