Pardon the mess of the posted code... but it should serve as an example:

protected void Page_Load(System.Object sender, System.EventArgs e)
  {

   if (Request.UserHostAddress != null)
    _ipAddress = Request.UserHostAddress;

   try
   {
    if (!Page.IsPostBack)
    {
     if (Session["AutoLogonProcess"] != null)
      return;
     else
      Session["AutoLogonProcess"] = true;

     string fullUser = Request.ServerVariables["LOGON_USER"];
     string userName = fullUser.ToLower().Replace(@"macu_nt\", "");
     // see if user is already logged in...
     if (this.UserInfo.UserID > 0)//this.User != null && this.User.UserID > 0)
     {
     }
     else
     {
      // otherwise, log them in
      UserInfo objUser = UserController.GetUserByName(this.PortalId, userName);

      if (objUser != null && objUser.Membership.Approved && !objUser.Membership.LockedOut)
      {
       UserAuthorized(objUser, false);
      }
     }
    }
   }
   catch (Exception exc) //Module failed to load
   {
    Exceptions.ProcessModuleLoadException(this, exc);
   }
  }

  private void UserAuthorized(UserInfo objUser, bool canProceed)
  {
   string strMessage = string.Empty;
   bool updatePassword = false;
   bool updateProfile = false;

   UserId = objUser.UserID;
   if ((!(objUser.Profile == null)) && (!(objUser.Profile.PreferredLocale == null)))
   {
    Localization.SetLanguage(objUser.Profile.PreferredLocale);
   }
   else
   {
    Localization.SetLanguage(PortalSettings.DefaultLanguage);
   }

   // check whether profile needs updating
   if (!updatePassword && this.RequireValidProfile)
   {
   }

   if (updatePassword)
   {
   }
   else if (updateProfile)
   {
   }
   else
   {
    // complete login
    UserController.UserLogin(PortalId, objUser, PortalSettings.PortalName, _ipAddress, false);
    try
    {
     int seconds = 0;
     string url = string.Empty;
     string port = Request.Url.IsDefaultPort ? string.Empty : ":" + Request.Url.Port.ToString();

     if (_hasRedirectUrl)
     {
      if (RedirectURL.IndexOf("http") == -1)
       url = "http://" + Request.Url.Host + port + RedirectURL;
      else
       url = RedirectURL;

     }
     else
     {
      url = "http://" + Request.Url.Host + port + Request.Url.Segments[0] + Request.Url.Segments[1];
     }

     Response.AppendHeader("Refresh", seconds.ToString() + "; URL=" + url); // give them a second or so to see the message, then redirect
    }
    catch (Exception ex)
    {
     AddModuleMessage(ex.ToString(), DotNetNuke.UI.Skins.Controls.ModuleMessage.ModuleMessageType.RedError, true);
    }
   }
  }