Unless your doing something like a shadow "spot" that's directly under the character and moves a little bit depending on the closest light source (but is still directly under the player), I can't think of a script you can use that would even make sub-par results. The only realistic way to make shadows of varying quality is with a shader, and with shaders, I barely have any experience. Look at some shader scripts, I'm pretty sure shadow scripts are out there free for you to use (providing you have at least a6).