How to modify existing Chess GUI

I want to modify an existing GUI so that it shows all the covered squares of each piece on the board.

Like this:

Only I want to see black´s covered squares as well

The idea is that will make it easier to learn basic chess patterns and internalize the movements of the pieces.

Here is a very crude animation that shows the general idea during an endgame scenario:
https://www.youtube.com/watch?v=3JEN2ADWj6g

1. Is it possible to modify an existing GUI?
2. How long would it take for a decent programmer to do it?
3. How the heck do they do it? 

Thanks

Will this work on a DGT board?

@learnthegoodmoves -  Sorry, no.

Learn computer code and you can do it yourself.  It comes more naturally to some than to others though.  Processing.org is a great resource to teach yourself, but its twice as easy if you have someone with a little experience to get started with.

:))

write about 20,000 lines of code like I did

i guess you could download the alpha version of the program from my website and use .NET Reflector to look at the C# code...

But you would find the code obfuscated (encrypted) like this...

for (int i = XXX.ZRO; i < (XXX.LOL * XXX.CQI); i++)

{

    WAR.PFN().ODF().FAU([i].WMF(

        WAR.VJF().IYG(WAR.PFN().ODF().FAU()[i], LCZ.CEX)

    );

    WAR.PFN().BEW().FAU([i].WMF(

        WAR.VJF().IYG(WAR.PFN().BEW().FAU()[i], LCZ.CEX)

    );

 }