gistfile1.txt

        private void button4_Click(object sender, EventArgs e)
        {

            while (lbCost.SelectedItems.Count > 0)
            {

                indexList.Add(lbCost.SelectedIndices[0]);
                lbCost.Items.Remove(lbCost.SelectedItems[0]);
            }


            for (int i = 0; i < indexList.Count; i++ )
            {
       

                totalCost -= Convert.ToDouble(shopList[Convert.ToInt32(indexList[i].ToString())].ToString());

                shopList.RemoveAt(Convert.ToInt32(indexList[i].ToString()));
                indexList.RemoveAt(i);

               
            }


           
               lblTotal.Text = Convert.ToString(totalCost.ToString("C"));

        }