how to conditionally return to form with messagebox yes/no

Question

I'm not sure how to handle returning to the form after this checkbox value check. My intention is to identify that two checkboxes were not selected and give the user a chance to go back to the form and choose if they click no on a messagebox. If they click yes, then proceed. What is the proper way to handle?

 private void btnConfirmCheckin_Click(object sender, EventArgs e)
        {
            string activity_log_id = txtactivity_log_id.Text;
            string CheckInTime = txtCheckInTime.Text;
            bool @bm = checkBoxBM.Checked;
            bool @ur = checkBoxUr.Checked;
            string activity_id = comboactivity_id.SelectedValue.ToString();

            if (checkBoxBM.Checked == false && checkBoxUr.Checked == false)
            {
                DialogResult dialogResult = MessageBox.Show("Nothing was selected for this outing.  Continue?", "Business Confirmation", MessageBoxButtons.YesNo);
                if (dialogResult == DialogResult.Yes)
                {
                    //user correctly chose nothing, wants to continue
                    return;
                }
                else if (dialogResult == DialogResult.No)
                {
                    //user made mistake, return to form and make a selection
                    
                }
            }


            AssignRescueActivity ara = new AssignRescueActivity();
            ara.SaveCheckin(activity_log_id, CheckInTime, bm, ur, activity_id);
            this.Close();
        }