Group Check / Apply Damage - making an exception for a nat20

Heya, in our game, if someone rolls a nat20 on a dex save they take no DMG / spell effect even if the spell says that they need to take half. Is there a way to make the DMG not apply on a NAT20?  Currently using this as my Apply DMG command: !group-check {{ --?{Save|Dexterity|Constitution|Wisdom} Save --process --subheader vs DC ?{DC} --button ApplyDamage !apply-damage ~dmg [[?{Damage}]] ~type ?{Damage on Save|Half,half|None,none} ~DC ?{DC} ~saves RESULTS(,) ~ids IDS(,) }} Hope someone can help! I am very new to this whole API stuff... 

I'm also new to this and would be interested in this as well. Specifically for PF2 creating a way to scale degrees of success (Crit success,  success, Failure, Crit Failure) with nat20/nat1's decreasing/increasing the degree of success by 1.  For now I just have to either manually update the damage, or adjust the HP for tokens that crit succeeded/crit failed.