I am trying to write a batch process to update drawings file to Restrict Top Level BOMs To One Configuration, but i'm getting a runtime error 91 at

boolstatus = Part.Extension.SetUserPreferenceToggle(swUserPreferenceToggle_e.swOneConfigOnlyTopLevelBom, 0, True)

what am I doing wrong???  Please see code below.

Option Explicit

Dim swApp        As SldWorks.SldWorks

Dim swModel      As SldWorks.ModelDoc

Dim sFileName    As String

Dim nFileName    As String

Dim Path         As String

Dim nPath        As String

Dim nErrors      As Long

Dim nWarnings    As Long

Dim Part         As Object

Dim boolstatus   As Boolean

Dim longstatus   As Long, longwarnings As Long

Sub main()

    Set swApp = Application.SldWorks

    Path = "D:\SolidWorks\Library" 'Change file path here

    Path = Path + "\"

    sFileName = Dir(Path & "*.slddrw")

    Do Until sFileName = ""

    Set swModel = swApp.OpenDoc6(Path + sFileName, swDocDRAWING, swOpenDocOptions_Silent, "", nErrors, nWarnings)

    Set swModel = swApp.ActiveDoc

    'Restrict Top Level BOMs To One Configuration

        boolstatus = Part.Extension.SetUserPreferenceToggle(swUserPreferenceToggle_e.swOneConfigOnlyTopLevelBom, 0, True)

         swModel.EditRebuild

       swModel.Save

   swApp.CloseDoc swModel.GetTitle

   Set swModel = Nothing

   sFileName = Dir

Loop

End Sub