TaskToCal is an Outlook Add-In which shows your Outlook tasks…

TaskToCal for Outlook

TaskToCal is an Outlook Add-In which shows your Outlook tasks in your Outlook calendar. Each time you create a new Outlook task with a due date a new Outlook appointment will be created, too.

If you modify the Outlook task in your calendar or in your task folder then this modification will be reflected in both your calendar and in your task folder.