I'm looking at modifying the measure tool and the mass properties tool to add functionality to it.  I want to add an internal volume for the mass properties tool.  I want to create a library part, a pipe, and include a custom property in that part: "Internal Volume".  When I select mass properties it will show up in the list of properties.  Not only will the mass properties show the volume of the part, but also the internal volume by taking the "Internal Volume" property from the part.

As for the measure tool, I want to add a "Length" property to the part.  If I select the part and click measure, the "Length" property will show up in the list.

Is there a way to do that with VBA?  Or do I have to go to C#?  Where should I start looking to modify the mass properties and measure?