BCGControlBar Pro for MFC
BOOL CBCGPProp::AddSubItem ( CBCGPProp pProp)

Adds a child item to the specifies property

TRUE if the new sub-property has been added successfully; FALSE if the same property does exist in the list of sub-items.

Call this function to add a sub-property to the specified property creating the hierarchical list of properties. The parent property becomes expandable and the property list control automatically displays a "plus" sign giving the ability to expand the item.

pPropSpecifies the sub-property to be added.