this is very simple .use update panel for label and in page load you change the string to display in label(i think you can write the code.and use one timer control for which you need to set target control id as update panel.event will be page_load.and set the time intervel.
you will get with out any extra lines of code
The thing is with "update panel" is that you have to download AJAXToolKit, and then you must enable your server to accept it, otherwise it will be problem after problem.
There is also a class called Timer that allows a function to be called at a set interval. When you add this AJAX functionality, set the Timer class to trigger it at every (30000) (30 seconds = 30,000 ms)