VB2010 Express Net MidiOutOpen Error

Imports System.Runtime.InteropServices
Public Class Form1
    Declare Function midiOutOpen Lib "winmm.dll" Alias "midiOutOpen" _
        (ByVal lphMidiOut As Int32, ByVal uDeviceID As Int32, _
         ByVal dwCallback As Int32, ByVal dwInstance As Int32, _
         ByVal dwFlags As Int32) As Int32

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) _
                            Handles Me.Load
        Dim lpMO As Int32
        Dim rv As Int32 = midiOutOpen(lpMO, -1, 0, 0, 0)
        Debug.Print(CStr(rv))

        '''''  the above code returns error 11 (MMSYSERR_INVALPARAM) ?? '''''
        '''''           -1 is the uDeviceID for the MIDI_MAPPER         '''''
        '''''  It also fails for uDeviceID = 0 (my on-board sound card) '''''
    End Sub
End Class