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Hi Amihay,
Please create a workflow rule on the Project Level. From the project you can access all of the work items - milestones and tasks. You can filter by the task name and update the name according to the changes to the project name. I am including a screen capture I created for you to show you the rule.
http://screencast.com/t/MieCpPCgsmX
Please let me know if you have any further questions.
Thank you,
Bea