Possible to macro arcane blast to crystal if its spawned?

[Sherrell]

I'm really annoyed on switching to crystal for A-Blasts and then to boss again for A-Missiles during PoF procs.
My clicking skills are poor and I usually click a stupid imp or something during a fight like mannoroth.

I was wondering if its possible to macro A-Blasts onto the crystal when it spawns without switching targets. Otherwise when the crystal is absent, it would cast A-Blasts onto your current target as normally.

I tried something like:

/cast [@Prismatic Crystal,exists] Arcane Blast

but it dosen't seem to work. Any tips? Is this possible?

[Komma]

Could probably make a macro that does /tar Prismatic Crystal and then /targetlasttarget to return after the cast.

[Curnivore]

Such things are considered auto-playing by Blizzard and unlikely to ever be supported. It's probably right because in a complex script they could probably auto-play a whole fight. What they could do is stop making rotations so complex by mistake

[Xyren]

why not do it the other way around? :p keep crystal in target and do /cast [@boss1] arcane missiles or use a focus target and a /cast[@focus] arcane missiles (thats what i do in combination with a mouseover set focus macro)