I have a NBarSeries chart with MultiBarMode = MultiBarMode.Stacked;
When my value is less than 100% (say -131%), the DataLabelStyle only shows -100%. 
Is there a way to specify my own custom formatting for DataLabelStyle?

Code snippet:
NBarSeries oBar = chart.Series.Add(SeriesType.Bar) as NBarSeries;      
oBar.InflateMargins = true;
oBar.Name = name;
oBar.MultiBarMode = MultiBarMode.Stacked;
oBar.WidthPercent = 30;
oBar.DataLabelStyle.VertAlign = Nevron.VertAlign.Center;
oBar.DataLabelStyle.TextStyle.BackplaneStyle.Visible = false;
oBar.DataLabelStyle.TextStyle.FontStyle = new NFontStyle("Verdana", 7.0f, FontStyle.Bold);
oBar.DataLabelStyle.Format = "<percent>";
oBar.DataLabelStyle.ArrowLength = new NLength(0);
oBar.DataLabelStyle.Visible = true;
oBar.Values.Add(.IsNull() ? 0.0 : value.Value);