BCGControlBar Pro for MFC
void CBCGPChartAxis::ShowMinorGridLines ( BOOL  bShow = TRUE)

Shows or hides minor grid lines.

Call this method to show or hide minor grid lines.

You can also call CBCGPChartVisualObject::ShowAxisGridLines to show major and minor grid lines for an axis at once.

bShowTRUE - show grid lines; FALSE - hide grid lines.