private void btnAdd_Click(object sender, EventArgs e)
        {
            if (lstProducts.SelectedIndex != -1)
                {
                    string itemChosen = lstProducts.Text.Substring(0, 15).Trim();
                    string itemPrice = lstProducts.Text.Substring(20).Trim();
                    txtItem.Text = itemChosen;
                    txtPrice.Text = itemPrice;
                    numItems = numItems + 1;
                    grandTotal += Convert.ToDecimal(txtPrice.Text);

                }
            else
                {
                    MessageBox.Show("Please select a product",  "Ron s Store" , MessageBoxButtons.OK, MessageBoxIcon.Error);
                    lstProducts.Focus();
                    
                }

       }