embed an MFC dialog-based app in a DLL and run using RunDll32

BOOL CAppInDllApp::InitInstance()
{
	// InitCommonControlsEx() is required on Windows XP if an application
	// manifest specifies use of ComCtl32.dll version 6 or later to enable
	// visual styles.  Otherwise, any window creation will fail.
	INITCOMMONCONTROLSEX InitCtrls;
	InitCtrls.dwSize = sizeof(InitCtrls);
	// Set this to include all the common control classes you want to use
	// in your application.
	InitCtrls.dwICC = ICC_WIN95_CLASSES;
	InitCommonControlsEx(&InitCtrls);
 
	// Standard initialization
	// If you are not using these features and wish to reduce the size
	// of your final executable, you should remove from the following
	// the specific initialization routines you do not need
	// Change the registry key under which our settings are stored
	// TODO: You should modify this string to be something appropriate
	// such as the name of your company or organization
	SetRegistryKey(_T("Local AppWizard-Generated Applications"));
 
   CWinApp::InitInstance();
 
	return TRUE;
}
 
void CALLBACK AppInDll_Entry(HWND hwnd, HINSTANCE hinst, LPCSTR lpCmdLine, int nCmdShow)
{
   AFX_MANAGE_STATE(AfxGetStaticModuleState());
 
	// Standard initialization
	// If you are not using these features and wish to reduce the size
	// of your final executable, you should remove from the following
	// the specific initialization routines you do not need
	// Change the registry key under which our settings are stored
	// TODO: You should modify this string to be something appropriate
	// such as the name of your company or organization
	/// SetRegistryKey(_T("Local AppWizard-Generated Applications"));
 
	CDlgInDll dlg;
   theApp.m_pMainWnd = &dlg;
	INT_PTR nResponse = dlg.DoModal();
	if (nResponse == IDCANCEL)
	{
		// TODO: Place code here to handle when the dialog is
		//  dismissed with Cancel
	}
 
}