I have a use case where when an opportunity hits a certain stage, say Pending, then tasks are created via workflow.  This works great.  But I also have a use case where if the opportunity moves to a further stage, say Closed Won, then the previous tasks are no longer necessary and I want them deleted without further action by the assignee.

Is there a way to do this out-of-the-box?  I am sure I can write an Apex trigger to do this, but it would require carnal knowledge of any workflows and I want this to be very configurable for my team in the future.  So, how can I clean up obsolete tasks?

Thanks in advance.