Reporting on Time Between Milestones

Hi there! I am trying to figure out the best way to use tasks/milestones as it relates to KPIs around implementation. We have a few key milestones throughout the deployment/implementation phase of our SaaS product and I want to build a dashboard that shows time between milestones or task completions. Ideally this does not use the “actual time” field but rather calculates the time between these time stamps (e.g. this project had an average time from milestone 1 to milestone 2 of 10 business days.) Is this something that can be done?