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In order to respond to user task selection you need to create the task with the NI_EVENT_MOUSE_LCLICK mask bit set in the EventMask field and you need to provide a NavigationItemUIInterface pointer that has a NavItemNotify function. When a user clicks a task then the framework calls your NavItemNotify function with the message value NI_EVENT_MOUSE_LCLICK.
If you have used the same same NavigationItemUIInterface for all of your tasks task items, you will need to distinguish them from each other. You can do this by the context data that was supplied when the item was inserted, the Navigation Path that the item was added with, or its alias. For example:
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