Turning a spell into a channeling spell...

How do I go about this?

More specifically, I would like it if divine shield could be turned into a channelin spell...

You can't change a spell into a channeling spell. However, to create a channeling Divine Shield, just base it of Big Bad Voodoo and change the targets to "self" only. Then change the animation to that of Divine Shield.

um, that doesnt work. Big Bad Voodoo seems to be hardcoded to prevent it from making the caster invulnerable.

Oh yeah I forgot the caster isn't targeted by BBV.

However, you could always base the spell on the spell called "Channel" and then add the invurnerability and animation with triggers.

There's a new event called Unit begins channeling a spell!
So just make him with a tranquility that doesnt heal or something like that, and when he begins to channel tranquility, attach a special effect and make him invulnerable, but when he is given another order (cancelling the spell) or a certain amount of time passes (whatever the channelling spells duration is) then it takes the invul and special effect off