/// <summary>
        /// Add To List function for the Dispense tab.  Adds an SKU to either the dispense or delete list, depending on the parameter
        /// </summary>
        /// <param name="_isdispensing">True if the user wants to add to the dispense list,
        /// false if the user wants to add the item to the delete list</param>
        private void D_AddToList(bool _isdispensing)
        {
            DataTable tempTable = new DataTable();
            DataTable ddTable;
            int       skuToAdd = 0;
            TextBox   ttb;
            ListBox   tlb;

            //Set the temporary controls depending on whether we're working with dispense or delete
            if (_isdispensing)
            {
                ttb     = tb_D_EnterSKU;
                tlb     = lbox_D_ToDispense;
                ddTable = dispenseTable;
            }
            else
            {
                ttb     = tb_D_EnterSKUDel;
                tlb     = lbox_D_ToDelete;
                ddTable = deleteTable;
            }

            try
            {
                skuToAdd = Convert.ToInt16(ttb.Text);
            }
            catch (FormatException)
            {
                return;
            }

            if (skuToAdd < 0)
            {
                return;
            }

            //See if the SKU exists in inventory, if not then return without doing anything else
            try
            {
                Mydb.SKUSearch(skuToAdd, tempTable);
            }
            catch (InvalidOperationException)
            {
                MessageBox.Show("Please open a database before attempting to dispense or delete glasses.",
                                "No Database Open", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
                return;
            }

            if (tempTable.Rows.Count == 0)
            {
                MessageBox.Show(String.Format("The specified SKU, {0}, does not exist in inventory.", skuToAdd),
                                "SKU Not Found", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
                ttb.Focus();
                ttb.SelectAll();
                return;
            }

            int i = tlb.Items.Count;

            //input is a valid SKU, find the best place to insert it into the listbox
            while (i > 0 && (int)(tlb.Items[i - 1]) >= skuToAdd)
            {
                i--;
            }

            if (i < tlb.Items.Count)
            {
                //input already exists, don't add anything else
                if ((int)(tlb.Items[i]) == skuToAdd)
                {
                    tlb.SelectedIndex = i;
                    return;
                }
            }

            //Insert item into list in the correct position and include it in the data table
            ddTable.Merge(tempTable);
            tlb.Items.Insert(i, skuToAdd);
            tlb.SelectedIndex = i;
            ttb.Clear();
            ttb.Focus();
        }