hmm... I just went to AU Optronics' web site to look up your model's specs and they didn't have it listed. They had the B156XW02 and B156XW04 but not the 03. And both of them are LED-backlit. In fact, I just looked up one site that claims to be selling your exact model number and version and the site claims your screen is LED-backlit as well.
My guess is that any version of the screen will work fine for replacement, if in fact your screen is LED backlit. However, if you are sure that yours is CCFL-backlit, then I would suggest only getting the exact version number since I don't know how the notebook would handle a different type of screen lightling.
edit: I've looked at a few shops now, and they all say that particular model has an LED backlight.
edit 2: even Asus says the screen has an LED backlight in the UL50Vt specs http://usa.asus.com/product.aspx?P_ID=QqP6p1vDWwn0IIzZ