pan and zoom window

I have a 3D scene and I want to move my scene preserving the current angle and continue operations(zoom, rotation etc) in new view. I am using gluPerspective and it seems to me like I need to translate along the line defining the axis on screen plane and I need the position of eye to calculate that translation axis. I feel I will have the same problem if I try to use a zoom window. How can I get the eye position? or how can I do this pan/zoom window operation? Does anyone know?