I'm trying to get a specific custom property of a selected part.  I found this discussion that claims to provide the answer, but when I try to use that in my code, I get errors: ​.

Here's the code I'm currently using:

Sub OpenSource()
    Dim lSuccess As Long, swModel As ModelDoc2, SourceURL As String
    
    Dim selMgr As SelectionMgr, Path As String
    
    With Application.SldWorks.ActiveDoc
        With .SelectionManager
            If .GetSelectedObjectCount2(-1) <> 0 And _
               .GetSelectedObjectType3(1, -1) <> 0 Then
                SourceURL = .GetSelectedObjectsComponent4(1, -1).GetModelDoc2.Extension.CustomPropertyManager("").Get("Source URL")
            End If
        End With
    End With
End Sub

This produces the following error on line 10:

Also, it would be very beneficial to know if the properties of a part set to lightweight are visible to the API.

Any help anyone can provide would be greatly appreciated.  I'm using SolidWork Professional 2015 on a Windows 7 machine.