Spell Edit help

[mordocai]

hey guys right now im making an edited black hole spell that drains the users mana, whenever he is using it. So basicly what i want is a channeling Black hole that drains the users mana for every seconds its in use? Any idea how to do this(i cant make a reverse knockback yet), so can anyone show/tell/make it for me?
EDIT:I will try to make one the post my triggers in an hour or so... sorry for starting this thread a bit early>>
Edit2: Ok so i have crudely made the spell, however whenever i try to learn it it just wont learn the spell! it becomes a blank icon, anyone know why? also here is test map, just to look through triggers if you have time i guess

 

[mordocai]

*bump*
for some reason no matter what i do when i learn the spell the icon will not show...