From Tracker Software PDF SDK
The NotifyTarget property allows the sending of messages of the e_Notify type from the current UI object to another UI object. If the current object's NotifyTarget property is not set explicitly, then any e_Notify messages will be directed to its nearest parent (if any).
For instance, dialog controls send their e_Notify messages to the dialog by default. To configure them to send e_Notify messages to each other, use the NotifyTarget property.
HRESULT get_NotifyTarget([out, retval] IUIX_Obj** pTarget); HRESULT put_NotifyTarget([in] IUIX_Obj* pTarget);