PS: DONOT bid over $20 as it will be rejected
You can code it in Java, .NET, PHP or make firefox/chrome browser addon/plugin/extension
Simply write a program that can refresh a list of URLs for every x seconds before moving on to the next url.
For E.g: A list of 10 URLs,
plugin/program refreshes URL1 for 10 times and then moves to URL2 and so on and stops refreshing till it completes the last URL in the list.