This example applies the Heading 1 style to each paragraph in the active document that begins with the word "Chapter."
For Each para In ActiveDocument.Paragraphs
If para.Range.Words(1).Text = "Chapter " Then
para.Style = ActiveDocument.Styles(wdStyleHeading1)
End If
Next para
This example opens the template attached to the active document and modifies the Heading 1 style. The template is saved, and all styles in the active document are updated.
Set tempDoc = ActiveDocument.AttachedTemplate.OpenAsDocument
With tempDoc.Styles(wdStyleHeading1).Font
.Name = "Arial"
.Size = 16
End With
tempDoc.Close SaveChanges:=wdSaveChanges
ActiveDocument.UpdateStyles