You must include the Virtual Panels header files in your modules. The top of your module may look so:
#include <vphead.h> // must be included first, contains #pragma hdrstop // all necessary standard headers #include <vpbase.h> // contains basics of Virtual Panels // Must be included in any case // These headers are optional. You must include them if you use: #include <vpbutt.h> // the button system #include <vpmenu.h> // the menu system #include <vpled.h> // the LED class #include <vpboard.h> // the Board class #include <vpoutbox.h> // the Outbox class #include <vpinbox.h> // the Inbox or TSInbox class #include <vpindic.h> // the Indicator class #include <vpgraph.h> // the Graph class