Calculate start date based on milestone

For our projects, they often are based around specific milestone event.  We have tasks leading up to that milestone, but then our project continues afterward with follow up actions to conduct surveys, review client feedback, and review our project team performance.  Since we use the forms with project templates, adjusting the project schedules from the template only work based on a start or end date, leaving us to calculate one of those for the rescheduling to be accurate across the entire project.  This calculation generally does not happen so we end up with a lot of manual rescheduling across some large projects.