5e Sheet Critting on Die Value Instead of Roll Value

Hi there. Instead of 1d20 as the core roll, I want to play with 2d10. That works just fine, it's neither here nor there. With 2d10 set as the core roll, and 20 set as the critical range, it does not register double 10's as critical. I know that adding [[ ]] makes it a single value, which works for the typical crit mechanic, but I want to see the individual die values when the result is less than 20. Is there any way to get it to do this?

No, there is no way to do this, without editing the roll20 sheet's roll template, and possibly adding custom roll parsing to the sheet workers. Roll20 has no native way to calculate citicals off two dice - its designed to only do this off a single die.

I never said it had to be natively supported. I have an API that has lets me do rolls, call the values later, and do math with them.  I am just having a hard time getting it to work as the core roll in the character sheet. Making a custom character sheet seems like it's beyond my ability though.

If you have access to the API you can probably do it it with that. But you can't do it using standard roll20 expressions. Making a custom character sheet might be overkill if you have the API, but this is in the character sheet forum so I answered assuming it was that kind of question.

I can't seem to get it to work, since it isn't accepting ! as the first character.  (), {}. and [[]] don't stop the error. Oh well. 

Some API script will work. But it might need to be written for your purpose. I can't really offer scripting suggestions, I leave that kind of thint to others. But they'll need to know what script you are using, and what exactly you want to do.