Visual Basic - Crear una ventena MDICHILD con SendMessage

Alguien me puede deicir si se puede Crear una ventena MDICHILD con
SendMessage en Vb. he adaptado un cobigo de C++;pero no funciona no me devuelve el hWnd de la ventana.le muestro el codigo en detalles.

Private Function MyCreateWindow(hPhwnd As Long, qa As Long) As Boolean
Dim mdi As MDICREATESTRUCT
Dim a As Long
Dim Mdies(Len(mdi)) As Byte

mdi.szTitle = "[Untitled]" & vbNullString
mdi.szClass = "myWindowClass"
mdi.hOwner = GetModuleHandle(vbNullString)
mdi.x = 0
mdi.cx = 100
mdi.y = 0
mdi.cy = 100
mdi.style = 1
´obtengo el hwnd de la ventena cliente
a = GetParent(qa)

RtlMoveMemory Mdies(1), mdi, Len(mdi)

hwnd = SendMessage(a, WM_MDICREATE, 0, ByVal Mdies(1))
If hwnd <> 0 Then
ShowWindow hwnd, SW_SHOWNORMAL
End If

MyCreateWindow = (hwnd <> 0)
End Function
Private Function MyRegisterClass() As Boolean
' WNDCLASS-structure
Dim wndcls As WNDCLASS
wndcls.style = WS_VSCROLL Or WS_HSCROLL
wndcls.lpfnwndproc = GetMyWndProc(AddressOf MyWndProc)
wndcls.cbClsextra = 0
wndcls.cbWndExtra2 = 0
wndcls.hInstance = App.hInstance
wndcls.hIcon = 0
wndcls.hCursor = LoadCursor(0, IDC_ARROW)
wndcls.hbrBackground = COLOR_WINDOW
wndcls.lpszMenuName = 0
wndcls.lpszClassName = "myWindowClass"
' Register class
MyRegisterClass = (RegisterClass(wndcls) <> 0)
End Function

Private Sub MyUnregisterClass()
UnregisterClass "myWindowClass", App.hInstance
End Sub