Making decisions based on dice roll results in macros

I am working on Coverting D&D Onslaught Board Game to Roll20.  My biggest issue is this in a macro Player attacks by rollling 2d20.  If either of the two dice is a nat 20, then it is a critical hit. If either of the two dice is not a 20, but one of them is a nat 1, the attack misses reguardless of other die roll. If neither the higher roll is the attack roll. Examples:    20 & Anything else = Critical Hit 1 & anything beside a 20 + miss Any other combo is rolled with advantage. The first one and the last one are easy to do in macro as they are determined by /roll 2d20kh1, but that does not consider if the die is a 1 or not. Thoughts?                  

I can do this with metascripts: !&{template:default}{{name=Onslaught Attack}}{{Roll 1=[[1d20]]}}{{Roll 2=[[1d20]]}}{{Result={&if $[[0]] = 20 || $[[1]] = 20}**Critical Hit!**{&elseif $[[0]] = 1 || $[[1]] = 1}**Miss!**{&else}{&if $[[0]] > $[[1]]}$[[0]]{&else}$[[1]]{&end}{&end}}}{&simple} That requires ZeroFrame and APILogic. Here are examples of the output:

You have to use a script, like Tim suggests. If you want to do this without a script, you need to show the numbers and let the GM and players decide, the way you would at a game table.

Thank you both