Help with trait
 

I am trying to make a macro for a trait and what I want it to do is alter the DEX max and reduce the arcane failure chance of a specific suit of armor, like chainmail. I cannot think of or find a trait or feat that does this. Can anyone help with the macro or point me to a feat or trait or such that does this?

I don't think you can create new macros. You might be best making an adjustment.
Arcane Armor Training (feat) reduces the Spell failure chance for armor you are wearing.
Armor properties like mithril increase the max Dex and lower Spell failure.

If this is for a specific set of armor, you could always make a "New (Copy)" of the existing chainmail, and alter the max Dex and Spell failure directly.

I meant script. Sorry.

Armor Expert is close to the idea. But I cannot figure out where it is telling to modify the armor types.