First, congratulations for finding the site with all the sales data in nice text format. I didn’t even know such a thing existed outside the MLS (well, Zillow has that, too, but can’t be accessed by a script because of those smarty pants codes buried in images).
And, second, for putting together a program to analyze the data. I’m assuming that it’s not THE Case-Shiller algorithm, as that must be proprietary stuff, but you should be pretty close if you follow their general prescription.