well, searched for the mod, didn't find it, but i did found something that can help the vampires under us. Vampire Daywalker Vampires no longer take sundamage. its all explainend on the page. You just need to place the file you have downloaded in the same folder as Oblivion.esm. didn't tested it myself but i already have two working plugins from the same site.
+ Put on the file in data files when you start the game <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" />
I saw a mod who did the thing you asked once, but i have no idea where it is...
