BCGControlBar Pro for MFC
UINT BCGM_ON_CHART_LEGEND_CONTENT_CREATED

The message is sent to the chart legend owner after legend was created or its content was updated.

Parameters
wParamthis parameter is not used
lParama pointer to CBCGPChartLegendVisualObject object.
Returns
the return value is ignored.

You should process this message to receive notifications from chart legend when a legend was created or updated.