BCGControlBar Pro for MFC
void CBCGPToolbarComboBoxButton::SetSelectionBarInDropDown ( BOOL  bSet = TRUE)
inline

Specifies whether the selected item will be drawn with the left-aligned selection bar. By default, the selection bar's presence is specified by the visual theme.

Parameters
bSetIf this parameter is TRUE, the vertical bar will be drawn on the left of the selected item.