How do I detect when an auto cast attack amplifier is cast?

[Ashcat]

Simple question in the title. What I mean is, how do i detect when a spell such as searing arrows or frost arrows is cast, because "starts the effect of an ability" doesn't seem to initiate the trigger.

 

[Ghan]

I don't know that it's possible.
There might be some JASS damage detection systems or the like that could help you. You might try searching around.

 

[Sil3nt]

You could use a boolean to keep track of autocast on/off
Unit is issued order with no target.
order = flamingarrowson
set flamingarrowson = true

Then have your basically check if the boolean is true before you do the actions. Note that this is not mui.