Put a button, a listbox, an openfiledialog on a form and set the following
events

  private void button1_Click(object sender, EventArgs e)
       {
           if (openFileDialog1.ShowDialog() == DialogResult.Cancel)
               return;
           listBox1.Items.Add(openFileDialog1.FileName);
       }

       private void listBox1_DoubleClick(object sender, EventArgs e)
       {
           System.Diagnostics.Process.Start(listBox1.SelectedItem.ToString());
       }

Nicolas Guinet