private void UpdateForm_Load(object sender, EventArgs e)
    {
        // TODO: This line of code loads data into the 'storeInvDataBase1DataSet.StoreInvDB' table. You can move, or remove it, as needed.
        this.storeInvDBTableAdapter1.Fill(this.storeInvDataBase1DataSet.StoreInvDB);

    }

    private void itemDropdown_SelectedIndexChanged_1(object sender, EventArgs e)
    {

        BindingSource newSource = new BindingSource();
        newSource.DataSource = storeInvDBBindingSource3;
        var itemID = itemDropdown.SelectedIndex;
        if (itemID == 1)
        {
            newSource.Filter = "Item = 'Coke'";
            quantityBox.DataBindings.Add("Text", newSource, "InStock");
        }
        else if (itemID == 2)
        {

            newSource.Filter = "Item = 'Diet Coke'";
            quantityBox.DataBindings.Add("Text", newSource, "InStock");
        }

    }