A button that zoom out the chart to previous selection because the button provided is zooming out it completely. I have added the a function (zoomOutPrev) for it along with some modifications in drop function and its working for me.

Here is the link for :

An HTML file used to test the function :

https://docs.google.com/open?id=0B_RgA2-RAxl0S2w0QmRvaHNfTmc

Edited Highchart Src :

https://docs.google.com/open?id=0B_RgA2-RAxl0VWt2X05HUzJVZlE