private void btnCheck_Click(object sender, EventArgs e)
 {
     try
     {
         SetCustomer();
         cust.Validate();
         MessageBox.Show(cust.ActualCost().ToString());
     }
     catch (Exception ex)
     {
         MessageBox.Show(ex.Message.ToString());
     }
 }
 public void Check()
 {
     try
     {
         SetCustomer();
         cust.Validate();
         MessageBox.Show(cust.ActualCost().ToString());
     }
     catch (Exception ex)
     {
         MessageBox.Show(ex.Message.ToString());
     }
 }