Check this thread:
http://forum.1cpublishing.eu/showthread.php?t=5189
if the thread alone is not informative enough - try contacting the guys who meddled with necromancy already - I wish you luck- I am great fan of necro army so necromancy could be much more interesting to me under specific circumnstances
For instance if it would really raise undead units from enemy fallen living / ex-living units (so one could increase his undead army numbers...)