updating aspx page from server

Currently I am working on a project where a web page will start a 3 hour data transfer process through the use of a web service. Basically a list of Id's are used to tell the web service to transfer an data object from one database to another.

When I start the process, I would like to allow the user to remain in control. He must be able to see how far the current process is, and be able press a cancel button to stop the data transfer. All this is run from an ASPX web page.

I have discovered that trying to run the process asynchronous does not allow me to update the user interface as I had hoped. Only when the entire process is finished Another problem I might face is that since the process takes a lot of time, the server objects might get refreshed at some point, which could cause me to lose my progress.

I am currently at the point where I am deciding whether or not to use the web server to process the data transfer. If I am, my current solution is to use tasks to run the process asynchronously, and use client side web calls (to the aspx page) to update the client interface. I am also implementing the IRegisteredObject interface for my work object. IRegisteredObject explanation

Any idea on how to best tackle this problem is most welcome. I really want to know if I'm heading in the right direction.