7vite, come va?
prova una roba di questo genere

codice:
sub Page_Load
		dim authcookie as HttpCookie
  		dim Ticket as FormsAuthenticationTicket
		try
			authcookie = Request.Cookies( FormsAuthentication.FormsCookieName )
			Ticket = CType( FormsAuthentication.Decrypt( authcookie.Value ), FormsAuthenticationTicket )
			response.Redirect( "pagina.aspx" )
		catch
			Ticket = new FormsAuthenticationTicket( 1, "valore", DateTime.Now, DateTime.Now, "false", 1 )
			dim encTicket as string = FormsAuthentication.Encrypt( Ticket )
			authCookie = New HttpCookie( FormsAuthentication.FormsCookieName, encTicket )
			Response.Cookies.Add( authCookie )
			response.Redirect( "pagina.aspx" )
		end try
	end sub