NodeXL's architecture is "layered," meaning that many features are reusable outside of our Excel Template application. That means you are going to have to modify more modules than if the graph metric features were hard-coded into the Excel Template.
Here is what you will need to do:
1. In the NodeXL\Algorithms project, add a MyGraphMetricCalculator class. Derive it from GraphMetricCalculatorBase. MyGraphMetricCalculator is application-agnostic; it knows nothing about the ExcelTemplate project.
2. Implement a MyGraphMetricCalculator.CalculateGraphMetrics(IGraph graph) method. Its return type is up to you; there is no standard return type for graph metrics.
3. In the NodeXL\ExcelTemplate project, add a MyGraphMetricCalculator2 class. Derive it from GraphMetricCalculatorBase2. MyGraphMetricCalculator2
uses MyGraphMetricCalculator to calculate your graph metrics, and then it formats them into Excel workbook columns.
4. In the NodeXL\ExcelTemplate project, add a MyGraphMetrics member to the GraphMetrics enumeration in GraphMetrics.cs, and read the "Important Note" at the end of the enumeration concerning what else you need to modify.
If you want to follow the pattern I established for the existing graph metrics, see the NodeXL\Algorithms\GraphMetricCalculators\VertexDegreeCalculator.cs and NodeXL\ExcelTemplate\GraphMetrics\GraphMetricCalculators\VertexDegreeCalculator2.cs classes.
That's probably the simplest of the graph metric calculators.