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