How to clear (remove) task start dates, due dates when a project is cancelled?

I know it's doable manually but if there are 100 tasks in a project then I have to perform 200 activities to clear start and due dates, I want to get that done by automation so that when a project status is changed to cancelled, all the start and due dates from all tasks should be removed automatically.

I think I have explained it in very very simple words but even after this explanation, please let me know if you have any further questions. But I need to get this done asap.