The mage macro I've seen the most is:

/stopmacro [channeling]
/use 13
/use 14
/use Gem (whatever the top mana gem is)
/use Presence of Mind
/use Focus Magic
/use Icy Veins
/castsequence reset=combat Arcane Blast, Arcane Blast, Arcane Blast, Arcane Blast, Arcane Missiles



You could try this as a click macro.
Something like:

/stopmacro [channeling]
/use 13
/use 14
/use Gem (whatever the top mana gem is)
/use Presence of Mind
/use Focus Magic
/use Icy Veins
/castsequence reset=combat ,,,,,,,Arcane Missiles
/use Arcane Blast

Then tweak the commas for 4x Arcane Blast, prior to the Arcane Missiles.