How to create a keygen in visual basic 2010

Just copy and paste this for the generate button :
TextBox1.Text = Int(Rnd() * 4)
Select Case TextBox1.Text
Case 0
TextBox1.Text = "Your code here"
Case 1
TextBox1.Text = "Your code here"
Case 2
TextBox1.Text = "Your code here"
Case 3
TextBox1.Text = "Your code here"
End Select