This report, particularly Chapter 3, provides a helpful overview for how to measure capacity building. It includes a detailed review of indicators, indices, tools and challenges for measurement, the command of which will greatly improve the quality of your work as an advisor.
"Like capacity, capacity building is a multi-dimensional and dynamic process. It should lead to an improvement in performance at each level and contribute to sustainability. The external environment also influences capacity building."
If you want to learn more about measuring capacity building, you'll find a useful link on this page to extra reading material regarding this topic