Maltab communication with VB.NET

Hello everybody, i'm trying to exchange data between Matlab and VB.NET I have realized a banal script called matlab_vd and collocated it in C:\Users\robim\Desktop (this is also the matlab current directory). The script is:

x = 2; 
y = 4; 

product = x*y

In vb.net i realized a simple form with a button and a text box. I want to run matlab script when i push the botton and print the value of product in the text box; so (following the documentation at https://it.mathworks.com/help/matlab/matlab_external/call-a-matlab-function-from-visual-basic-net-client.html ) i wrote this in visual studio:

Public Class Form1
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim MatLab As Object
        Dim Result As String
        MatLab = CreateObject("Matlab.Application")
        Dim acquired_value As Single

          Result = MatLab.Execute("cd C:\Users\robim\Desktop")
          Result = MatLab.Execute("matlab_vb")
          MatLab.GetFullMatrix("product", acquired_value)

          TextBox1.Text = acquired_value.ToString

      End Sub
  End Class

However this code doesn't work. I have opened matlab and executed the visual studio app but i have an error at:

MatLab.GetFullMatrix("product", acquired_value)

I'm new with vb; do i need to add some libraries to my vb code? have i made a mistake in the code? Can someone give me any advice? Thanks a lot guys!