public void cbPeriodChange(object sender, EventArgs e)
        {
            int itemIndex = cmbPeriod.SelectedIndex;

            if (itemIndex != 0)
            {
                if (itemIndex != 1)
                {
                    if (itemIndex == 2)
                    {
                        fSession        = -1;
                        txtSession.Text = "";
                    }
                }
                else
                {
                    fSession        = -1;
                    txtSession.Text = "";
                }
            }
            else
            {
                fSession        = PIBUtils.GetSession(DateTimePicker1.Value);
                txtSession.Text = Convert.ToString(fSession);
            }

            RefreshTrends();
        }