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.
Disclaimer: All the downloads are provided as-is, without any liability to losses occurred because of the usage.