Recalculating start and due dates of tasks when a specific date field changes on a separate list

Hi,

I have a custom list that contains project-related information as well as due dates on project milestones. I will be creating tasks using these project milestone due dates using workflow. Now here's the challenge: The due dates can be updated any time. I would like to update the task start and due dates if someone changes the dates within the custom list. 

One other option I can think of is to integrate tasks with the custom list. Is this possible? 

I only have SPD so I appreciate if someone can point me to the right direction.

Thanks!