In typical human-computer interaction, users convey their intentions through traditional input devices (e.g. keyboards, mice, joysticks) coupled with standard graphical user interface elements. Recently, pen-based interaction has emerged as a more intuitive alternative to these traditional means. However, existing pen-based systems are limited by the fact that they rely heavily on auxiliary mode switching mechanisms during interaction (e.g. hard or soft modifier keys, buttons, menus). In this paper, I describe the roadmap for my PhD research which aims at using eye gaze movements that naturally occur during pen-based interaction to reduce dependency on explicit mode selection mechanisms in pen-based systems.