private void btnBack_Click(object sender, EventArgs e)
        {
            StartUpForm startUpForm = new StartUpForm();

            this.Hide();
            startUpForm.ShowDialog();
        }
        private void btnBack_Click(object sender, EventArgs e)
        {
            this.Close();
            StartUpForm startUpForm = new StartUpForm();

            startUpForm.Show();
        }