Macros to auto reroll to confirm

is there a macro so that if you roll a nat 20 or whatever it auto rerolls a d20 to see if it confirms?

Not really. You can set up your roll to explode on a 20 but it won't show it separate from the first roll. You best bet is to make a macro with two rolls and just ignore the second roll if you don't roll a nat 20 on the first. You might be able to get an API script made for it but I'm not sure on it. You would need to ask about that in the API forum section.

Possible with API support. I have just the thing in my basic attack script (although I do not use diceroll outputs I use randominteger(max))

I find it works simply enough to just include the confirm rolls and damage within your regular attack macro. The specifics will of course vary quite a bit between game systems. Ex: /me takes advantage of his enemy's distraction and launches a SNEAK ATTACK with his short swords! [DualWielding] MAIN:[[ 1d20 + 3 +1 ]]|[[ 1d20 + 3 +1 ]] for [[ 1d6 + 3 +1d6 ]](P) Dmg -----If Crit :+[[6]](P) Addt'l Dmg OFF:[[ 1d20 + 3 +1 ]]|[[ 1d20 + 3 +1 ]] for [[ 1d6 ]](P) Dmg -----If Crit :+[[6]](P) Addt'l Dmg Results in: Dorrin: [DualWielding] MAIN:12|22 for 9(P) Dmg -----If Crit :+6(P) Addt'l Dmg OFF:19|21 for 5(P) Dmg -----If Crit :+6(P) Addt'l Dmg