Detect if a unit is still casting a spell

[SAUS]

I have a spell that is channelled that does some trigger stuff periodically. The trigger stuff should immediately stop if the unit stops channelling the spell. Is there some way to detect if the unit is still channelling the spell?

I would imagine it has something to do with unit orders. Anyway, the spell is based off of starfall.

EDIT:
I am perfectly fine with the stopping part. I can handle everything else, I just want to know what check can be made to see if the unit is still channelling the correct spell.

 

[WereElf]

Doesn't "Unit stops casting an ability" work for detecting that?

 

[SAUS]

Doesn't "Unit stops casting an ability" work for detecting that?

I haven't tried it. If it's that easy, it will be nice lol Anyway, I will test solutions when I get the chance.

 

[Zwiebelchen]

Unit stops casting should work. However, it will also fire when the spell finished channeling (without getting interrupted), keep that in mind.

 

[SAUS]

Unit stops casting should work. However, it will also fire when the spell finished channeling (without getting interrupted), keep that in mind.

That's perfect. I suppose I could even just not have an end case for the periodic effect other than detecting when the unit stops casting.