Quest Tracker
 

Does anyone know of a quest tracker that encompasses a data base or spreadsheet format like Excel?

Do you mean a UI mod, or just anything in general?

UI Mods can't write to files (except your log obviously) so you'd need outside software to do that. So long as it doesn't actually read anythign from teh game or alter the game, but just uses your log it would be ok, but anything more than that begins to violate the EULA.