How to use cookies to store Google map changes to help create aback-to-last-extent button?

Hello,

I want to add a button to my Google Maps site, that will allow users
to cycle back through all the previous map extents that they have
visited (the map extent would change when they pan or zoom the map).

I understand that i would need to save these map changes (bounding-box
coords, zoom level and map type) in a cookie that persists while the
user remains at the site - beyond that i have no idea how this might
be implemented so any help you can provide would be most welcome.



Many thanks