This ones a bit complicated since VP and DP values can change without core assistance (aka buying DP through the website/voting). To do this properly you'll need a hook on buy event and on vote event through your website. There's probably a callback somewhere on whatever CMS your using that you can work into your core. You'll also want to load values in on core startup and on buy event ingame from a vendor.
The amount of ExtendedCurrency you'll have will be set through a few basic lines of code.
With the On buy event from the vendor, you'll want to remove VP/DP from the player through some method you'll be making via a mod in Player.cpp
(You could also pull dp/vp values constantly every couple seconds from db, but seems like resource wasting)