The Firefox add-on seems to work rather simply. Here are instructions on how to do it:
1. If you don't have Mozilla Firefox, download the latest version (3.6.3). 2. Open Firefox browser and go to Tools-->Add Ons. 3. Select the Get Add-ons toolbar icon and in the search box enter ReloadEvery and hit Enter. 4. Select ReloadEvery and install the add-on accordingly. 5. Restart Firefox and call up your chart on StockCharts.Com. 6. Right click on the window and the menu should include the ReloadEvery option. 7. From that menu you can select the Reload Every 5s option.