custom authentication and Request.isAuthenticated

[Guest]

Hi,

I am working on an application and want to set a cookie so that
on a page when I check 'Request.IsAuthenticated', it would give me the
correct value.

How can I set the Authentication cookie?
I tried...
FormsAuthentication.SetAuthCookie("myUserName", false);
after the user has successfully been authenticated, but it doesn't work.

Pls help