Simple API but I can't get it to work (GetAppliedGPOList)

If one of you API gurus could look at this module and tell me what I am doing wrong I would appreciate it. This should be pretty straight forward and it's executing without errors but nothing is being returned.

(I purposely put the 'stop' in there so I could evaluate the returned results)

VB Code:

Module Module1
    Const GPO_LIST_FLAG_MACHINE = &H1
 
    Private Structure GROUP_POLICY_OBJECT
        Public dwOptions As Integer
        Public dwVersion As Integer
        Public lpDSPath As String
        <VBFixedString(50)> Public lpDisplayName As String
        Public szGPOName As Byte()
        Public GPOLink As Integer
        Public lparam As Integer
        Public pNext As IntPtr
        Public pprev As IntPtr
        Public lpExtensions As String
        Public lparam2 As Integer
        Public lpLink As String
    End Structure
 
    Sub Main()
 
        Dim obj As IntPtr = Nothing
        Dim retval As Boolean = GetAppliedGPOList(GPO_LIST_FLAG_MACHINE, Nothing, Nothing, Nothing, obj)
 
        Stop
 
    End Sub
 
 
    <System.Runtime.InteropServices.DllImport("userenv.dll", EntryPoint:="GetAppliedGPOListA")> _
    Function GetAppliedGPOList(ByVal dwflags As Integer, ByVal pMachineName As String, ByVal pSidUser As IntPtr, ByVal pGuidExtension As IntPtr, ByRef ppGPOList As IntPtr) As Boolean
    End Function
 
End Module