Channeling via Triggers

[NightStalker]

I was wondering on how to create this but couldn't find a tutorial or spells, I know I must not have looked well.

Can someone just make a very simple channeling ability, possibly a very simple one, just to show me how, based of from Channel ability will be great for me btw.

If you don't want to do it at least link me a spell with GUI triggers.

Thanks!

EDIT: If anyone is feeling generous, you can help me further by making the spell's base.

The unit will channel and then will slide a stragihtforward path damaging everyone, it would be good if the path it will slide was shown like a sign appearing there or something else, a sloppy one is nice too, just make the channeling part clear to me

 

[Maker]

Use a combination of casting time and follow through time, the data fields in Channel.

Casting time = time between giving the order and starting the effect.
Follow through time = time between starting the effect and finishing casting.

 

[NightStalker]

So if i want the channeling to be 3seconds cating time should be 3 seconds. No need to trigger the channeling.

I saw tank commander's Boss Ultimate Pack, he used a channeling system why did he need that then?

EDIT: I finished the spell but casting time is like a no turning back channel effect, for 3 seconds the unit can't move but a normal channeling must be cancellable