How To Get A Random Number To Count Down

I am trying to get a random number to count down to zero, but what i have keeps giving me a random number. Then every second it will generate a new random number between 4 and 11, and won't count down. if anyone can help it would be greatly appreciated. thanks in advance!

enter code here

            private void timer1_Tick(object sender, EventArgs e)
    {

        Random nuber = new Random();
        i = nuber.Next(4, 11);
        i--;

        textBox1.Text = i.ToString();

        if(i == 0)
        {
            Form1 f1 = new Form1();
            Form2 f2 = new Form2();

            f2.Show();
            f1.Close();
        }

    }