How to format a number string in gridview?

// Handle the grid's RowDataBound event
MyGridView.RowDataBound += new GridViewRowEventHandler(MyGridView_RowDataBound);

// Set the value to x / 1000 in the RowDataBound event
protected void MyGridView_RowDataBound( object sender, GridViewRowEventArgs e )
{
    if( e.Row.RowType != DataControlRowType.DataRow )
      return;

    // Cast e.Row.DataItem to whatever type you're binding to
    BindingObject bindingObject = (BindingObject)e.Row.DataItem;

    // Set the text of the correct column.  Replace 0 with the position of the correct column
    e.Row.Cells[0].Text = bindingObject.ProcessingTime / 1000M;
}

GridView.DataSource = ....

BoundField total = new BoundField();
total.DataField = "Total";
total.HeaderText = "Total Amount";
total.DataFormatString = "{0:C}";
donations.Columns.Add(total);

......

String.Format("{0:0.000}", test/1000);

try
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        if (((DataRowView)(e.Row.DataItem))["Columnname"].ToString().Equals("Total", StringComparison.OrdinalIgnoreCase))
        {
            e.Row.Font.Bold = true;
            //-----or ant thing you want to do------
        }
    }
}
catch (Exception ex)
{

}