AJAX :: Real Time Progress Bar With Dynamic Task State?

I'm trying to create custom control which displays real-time state (progress bar, or percent value) during time-consuming task (no animated GIF, or static text message).

This scenarion can't be done with standard UpdateProgress control, because it displays only static progress information.

This custom control can be then used as follows:

Aspx page should contain this custom progress control and a button.When user clicks button, page executes postback to the server.Server in button click handler starts performing some time-consuming task. Client installs timer with interval is set to 2000 ms.In client timer event handler should be request to the server for progress refresh.If server receives request from progress control, it checks actual task progress state, and performs client control refresh.When server terminates executing the task, it hides progress control on the client.

How can be this scenarion accomplished? How can I create such custom control?