Help with an API function im trying to write

I am trying to write an API function and was wondering if somebody can look it over and let me know what I am doing wrong. I am trying to return a handle and it just returns 0 every time. I have scoured the net but can't find any examples at all


    Private Structure DS_SCHEMA_GUID_MAPA
        Dim GUID As Guid
        Dim GUIDType As Long
        Dim pName As String
    End Structure


    Private Declare Function DsMapSchemaGuidsA Lib "ntdsapi" (ByVal hDS As Long, ByVal cGuids As Long, ByRef rGuids As Guid, ByRef ppGuidMap As DS_SCHEMA_GUID_MAPA) As Long
    Private Declare Function DsBindA Lib "ntdsapi" (ByVal DomainControllerName As String, ByVal DnsDomainName As String, ByRef phDS As IntPtr) As Long



    Private Sub testy()
        Dim retVal As Long
        Dim MyHost As String = System.Net.Dns.GetHostName
        Dim handle As IntPtr
        Dim t As New Guid("{2BEC133B-AE2B-4C32-A3F5-036149C4E671}")
        Dim temp As New DS_SCHEMA_GUID_MAPA

        retVal = DsBindA(vbNull, vbNull, handle)
        MsgBox(retVal.ToString)
        MsgBox(handle.ToString)
        DsMapSchemaGuidsA(handle, 0, t, temp)

        MsgBox(temp.pName)
    End Sub

retVal returns a code but this reference http://msdn.microsoft.com/en-us/library/ms675931(VS.85).aspx does not say what events are which code? Where can I obtain this information?

Handle returns 0. Probably because I have an error code in retval but no way to tell whats being thrown back to me


Im a bit lost on this if somebody would please help me!!