Nantonos, you gem.
The article you link to is a bit general and essentially tells you how to find out a single declination for where you are currently so that is not so helpful.
HOWEVER, the library you link to is based on this post (says so in the comments of the code). This guy has tried to do exactly what I was going to attempt. This didn't work so well so he wrote his own software that he can update using the NOAA tables. It looks like he has updated it since the last table was released so I should be good for the next 3 years. I am going to give this library a go.
Thank you so much!