Understanding the Rerolling Dice (B,F) and Special Case: Reroll Once (B,F)

So I'm reading about these and maybe I'm over looking a simple solution but I'm not getting how to make this work for pathfinder. I want a player to be able to make macro that can roll their attack roll, roll their damage, and then reroll the attack dice again on a 1, or anything with in the weapons critical threat range, but only once (the confirmation). It seems like it should be: Longsword: [[1d20+16ro<2ro>=18]] for [[2d6+19]] I'm assuming syntax here though.

It's unfortunately not possible to specify multiple ranges of "reroll" target numbers. As such, I would suggest you use [[ 1d20ro>18 + 16 ]] and manually reroll any natural ones.

For future reference < always means "lesser than or equal to" and > always means "greater than or equal to" in the dice rolling syntax, there's no need to use ">=". Also, if you want to check for natural 1's or crits, you should put the modifier on the 1d20, not on the flat 16 bonus. Oddly, it is possible to specify multiple ranges on a regular reroll (keep rerolling until you get a different number), but not on "reroll once". So this would be valid: Longsword: [[1d20r<1r>18+16]] for [[2d6+19]] Except that a 1 or 18-20 will continue being rolled until a 2-17 is rolled. But you can hover over the result to see if that happened and interpret the results appropriately.

Thanks everyone!