private void btnOk_Click(object sender, EventArgs e)
        {
            if (is_Validate())
            {
                try
                {
                    de.AddNHIFRate(
                        decimal.Parse(txtFromAmount.Text.Trim()),
                        decimal.Parse(txtToAmount.Text.Trim()),
                        decimal.Parse(txtRate.Text.Trim()));

                    NHIFRates f = (NHIFRates)this.Owner;
                    f.RefreshGrid();
                    this.Close();
                }
                catch (Exception ex)
                {
                    Utils.ShowError(ex);
                }
            }
        }