static BOOL CALLBACK HandleChildWindow(HWND hChildWindow, LPARAM Param) { PostMessage(hChildWindow, WM_KEYDOWN, VK_NUMPAD1, 0); return TRUE; } void SimulateKeyDown() { HWND hCalcWindow = FindWindow(NULL, "Калькулятор"); if (hCalcWindow != NULL) { EnumChildWindows(hCalcWindow, &HandleChildWindow, 0); } }