how to paint cells in gridview in dynamically

void radGridView1_CellPaint(object sender, Telerik.WinControls.UI.GridViewCellPaintEventArgs e)
{
    GridDataCellElement dataCell = e.Cell as GridDataCellElement;

    if (dataCell != null && dataCell.ColumnInfo.Name == "UnitPrice")
    {
        double value = Convert.ToDouble(dataCell.Value);
        if (value == 0)
        {
            return;
        }

        Brush brush = value < 20 ? Brushes.Red : Brushes.Green;
        Size cellSize = e.Cell.Size;

        using (Font font = new Font("Segoe UI", 17))
        {
            e.Graphics.DrawString("*", font, brush, Point.Empty);
        }
    }
}