private void btn_next(object sender, EventArgs e)
 {
     cr_dr_detail u = new cr_dr_detail();
     u.Show();
     this.Hide();
 }
 private void button4_Click(object sender, EventArgs e)
 {
     cr_dr_detail cr1 = new cr_dr_detail();
     cr1.Show();
     this.Hide();
 }