Adding a die on a crit

Probably simple, but I have not been able to figure it out. I have this current macro: &{template:default} {{name=@{character_name} - Greataxe}} {{attack=[[1d12+5]] vs Deflect}} {{damage= [[3+1d10]]}}  On a crit on the d12 I want it to roll an additional die of damage. Is there a way to detect that and carry it over into the next roll?

Ok, I don't know what your crit threshold is, but I made an assumption that it is "12" on the d12. If it is otherwise let me know and I can tweak it.  Also, I assumed you would want to add the crit damage to the original damage? If it is otherwise let me know.  &{template:default} {{name=@{character_name} - Greataxe}} {{attack=$[[0.computed]] vs Deflect}} {{damage=[[3+1d10+1d10*[[{[[1d12+5]],0}>[[12+5]]]][crit]]]}} What the macro does:  Attack: 1d12+5 Damage: 3+1d10 +1d10 if the d12 was a 12. 

That does it! Thanks!