Browser Event and Authentication (IE)

I'm working on a viewer that uses the Microsoft Webbrowser Control (COM Control).
At start I navigate to a website that requires authentication to be viewed.
In IE a window would appear that asks you for the username and the password.
In my app I want to catch that event and send those authentication parameters by myself so that a custom window of my app appears and not the authentication window from IE.

Any ideas to this?

thx in advance!