AutoCAD 2010 :: Open And Create A Drawing In 2012 From Visual Basic 2010

I'm doing a program in Visual Basic 2010. In one of the forms I put a button that when clicked must open AutoCAD 2012 and make a drawing in it. The user will decide where to save it.The steps are these:

1. I added the references Autodesk.AutoCAD.Interop and Autodesk.AutoCAD.Interop.Common to the Visual Basic Project. That's OK.

2. I wrote this in the heading of the form's

- Imports Autodesk.AutoCAD.Interop
-Imports Autodesk.AutoCAD.Interop.Common

3. In the event Click of the Button1 I put this:

    Dim acadApp As New AcadApplication 'Create an instance of an AutoCAD Application
    AcadApp.Application.Visible = True 'Show the instance of the AutoCAD Application
    Dim acadDoc As AcadDocument 'Create an intance of an AutoCAD Document
    acadDoc = acadApp.Documents.Open("C:Respaldo TesisDibujo2.dwg") 'Open a Document called Dibujo 2
    'Draw a line
    Dim PT1(2) As Double
[code].....