static private void SelectFormula_Click(object sender, EventArgs e)
        {
            TextBox tb = (TextBox)((Button)sender).Tag;

            tb.Text = ChartWinControl.DoSelectFormula(tb.Text, null, true);
            tb.Focus();
        }
        private void btnMore_Click(object sender, System.EventArgs e)
        {
            string s = ChartWinControl.DoSelectFormula(null, null, false);

            if (s != null)
            {
                AddFormulas(s);
            }
        }