Using Order conditions with spells

Wondering if you could detect spells being cast from event - unit issued order. Since the order condition can be filled with anything it seems there would be a way to detect spells. This may not be hugely useful to the average mapper, but for several abilities it would save about 15 minutes of trigger work to be able to detect when immolation'ish abilities are turned off. Also you could stop an ability before it was cast, whereas currently you can only detect when it has begun casting, which is too late. Any ideas?

Why use "order" when u can check if a spell is being cast? i think u can use "a unit begins casting a spell" and then check if it is immolation. And, of course, the same when turning off, except u use "a unit stops casting a spell".

Not?

If the ability has an order string, you can catch the order. With immolation, there is no button pressed when it runs out of mana, thus no order.