private void CheckSelectedRate(ComboBox comboBox)
        {
            Rate selectedRate = (Rate)comboBox.SelectedItem;

            if (selectedRate != null)
            {
                if (selectedRate.Value == -1)
                {
                    _selectedComboBox = comboBox;

                    frmCustomRate frmCRate = new frmCustomRate(this);
                    frmCRate.ShowDialog(this);
                }
            }
        }
        private void CheckSelectedRate(ComboBox comboBox)
        {
            Rate selectedRate = (Rate)comboBox.SelectedItem;
            if (selectedRate != null)
            {
                if (selectedRate.Value == -1)
                {
                    _selectedComboBox = comboBox;

                    frmCustomRate frmCRate = new frmCustomRate(this);
                    frmCRate.ShowDialog(this);
                }
            }
        }