Multiple Rotating Homepages

Hi: Using firefox I know you can set up multiple homepages that open in different tabs, but what about setting a few homepages that then rotate through on  an open browser, say every 20 seconds or so? There are six or so sites I go to throughout the day and it would be nice if I have a browser open behind my work if it's rotating through those six so that I can catch each of them from time to time rather than having to click between them.
 
Simon.