I'll probably get this answer to this by experimenting a bit later on anyway but can anyone tell me how I can get a piece of javascript to run before the rest of the page has loaded or before it has even started to load?

Any help would be greatly appreciated

maybe you could try using onFocus (when the window is active) instead of onLoad? and then have the script programmed to loop only once (in case the event onFocus were to happen more than once).