You can download the latest version of my excel based IP functions here.
Download & extract this file to get the RBIPFx.xla file.
For procedure to install the add-in check this post.
I have also added a presentation to explain the latest functions. You can view that here
Latest version is 0.3. It includes function for IP address manipulations and verification.
As many people have asked for the source code. I have included it in the Gitub.
Disclaimer: All the downloads are provided as-is, without any liability to losses occurred because of the usage.