Try the following saved in the normal template (which is normal.dotm, not normal.dotx).
The normal template must also have the named style
The message boxes are there for information only while testing. They can be removed along with the 'Else' branch of the conditional statement.
New documents based on the normal template will have the style.

Sub AutoOpen()

Dim strMyStyle As String
Dim oStyle As Style
Dim bFound As Boolean
    strMyStyle = "MorzNum"
    For Each oStyle In ActiveDocument.Styles
        If oStyle.NameLocal = strMyStyle Then
            bFound = True
            Exit For
        End If
    Next oStyle
    If Not bFound = True Then
        MsgBox strMyStyle & " Style added to the document"
        Application.OrganizerCopy _
                Source:=ThisDocument.FullName, _
                Destination:=ActiveDocument.FullName, _
                Name:=strMyStyle, _
                Object:=wdOrganizerObjectStyles
    Else
        MsgBox "The style " & strMyStyle & " already exists in the document "
    End If
End Sub