Possibility of tracking realtime game statistics with 3rd party applications

Recently I have been recording all of my statistics post-game into excel sheets to make them more comprehensive and meaningful to the eye and I had an idea of writing a program which would, in real time, record all the known data to the player into a some form of table. It could also be implemented into a game as an extra table (just like the score one) - to see things such as you minion/minute rate, etc. I'm a first year programming student and never tried anything of this sort, so I was curious as to whether a) it's legal to do this from Riot's perspective b) you have any tips on what to use to read the values from League client and save them somewhere else, since at the moment I have no idea how such a project could be done.