This function provides the default behavior for a secondary window.
#define INCL_SW #include <os2.h> HWND hwnd; /* Dialog window handle. */ ULONG msg; /* Message identity. */ MPARAM mp1; /* Parameter 1. */ MPARAM mp2; /* Parameter 2. */ MRESULT rc; /* Returns MRESULT. */ rc = WinDefSecondaryWindowProc(hwnd, msg, mp1, mp2);