Selections to populate min/max variable

Hi, I just started using Bokeh today and really like it. I’m struggling to do something that is likely very primitive.

In this notebook:
http://nbviewer.ipython.org/github/benbowen/openmsi-programmatic-access/blob/master/Chapter2/Chapter2_DiggingIntoTheData.ipynb

In the Bokeh plot at the bottom of the page, a user would like to use the selection box to specify a region of “m/z”. This would effectively specify the value of mz_min and mz_max that I could use for later analysis.

I’m searching the docs and not finding the relevant sections. Can you point me in the right direction?

Thanks,

Ben