protected void txtchalan_TextChanged(object sender, EventArgs e)
    {
        bool Auth = Specimen.GetChallanNoAuthentication(txtchalan.Text.Trim());

        if (Auth)
        {
            MessageBox("Challan no is already present");
            txtchalan.Text = "";
            txtchalan.Focus();
        }
        else
        {
            txtChalDate.Focus();
        }
    }