[Trigger] Unit Mana as an event

[BooK2]

Ive got a probelem i need a trigger to start with a units mana reaching 0 the problem is that the unit is part of a unit array and i need it this way for the rest of the triggers to work so far ive been using a non unit array with a periodic trigger that keeps updating the ammount of mana a unit has! that works fine but i need it to be in a unit array or the map wont work properly if anyone could help it would be greatly apreciated! srry this question sounds stupid but im new to wc3...

Oh yeah and one more thing im having a bit of trouble with the spell book well 2 more things
my first problem is whenever i cast a spell using my custom one my mana is allways put down to 10-11 from 100-200 mana when im using a 35 mp spell all the spells cause a trigger to go off to create an item. and the second thing is i want my spell book to get more spells the more i upgrade it through a talent tree i made the talent tree works off normal upgrades...