can someone help me with a channeling modifier?

I am not too hot at writing macros and wondered if anyone could help me out:

I want a macro to use for close range aoe - that will start hellfire (channeled) on my locks and cast Arc Explosion (Instant) on my mage on the same button.

At the moment every time I hit my H Key the locks re-start channeling their hellfire (waste of mana).

So how would I have - Cast Hellfire if not already, but if hellfire is already being channeled do nothing, cast Arcane Explosion every button press. (second part is easy just keybind AE to H)

many thanks in advance

simply add the nochanneling option to the macro

eg

Code:

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/cast [nochanneling] Rain of Fire

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I knew it would be easy - thanks djarid

For more fun spam, can try

Code:

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/stopmacro [channeling]
/cast Hellfire()
/say Burn baby, burn!

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:P