BCGSuite for MFC
BCGCBPRODLLEXPORT UINT BCGM_ON_CHART_MOUSE_DOWN

The framework sends the BCGM_ON_CHART_MOUSE_DOWN message when the chart visual object receives a mouse button down notification.

Parameters
wParamID of chart visual object.
lParama pointer to a BCGPChartHitInfo structure.
Returns
TRUE - disable further mouse down processing. In this case zoom /pan/selection will not occur (if enabled).

You should process this message to implement interactive charts.