Hi,
One possible way to accomplish what you are trying to do is to have your form defaulting to a View where you check your user credentials (Login View). If your user passes your test (use name / passord, etc.), you can then Switch View and go to what you currently have as a default View in your form. Else, you can safely warn your user and close the form...
Hope that it helps.
Regards,
Franck Dauché