BCGControlBar Pro for MFC
void CBCGPChartSeries::SetSeriesLineWidth ( double  dblWidth,
int  nDataPointIndex = -1 

Sets line width either for all series lines, or for specified data point.

Use this method to set line width for series lines. If nDataPointIndex is -1, the specified line width will be used for all data points that have not been formatted individually.

dblWidthSpecifies the new line width.
nDataPointIndexSpecifies a data point index. Use -1 to set the option for a series.