[Help] A way to recieve a numerical result depending on the number in the dice roll?

Greetings, Not the first time posting here, and actually i received a very good tip, but later i discovered an issue that i will adress later in this text. I'm developing a homebrew system, I won't go deep on how the whole thing works out, but basically is based on the result of a d20 die;When the d20 rolls from 12 to 15 the player deals 1 point of damage, from 16 to 18 the player deals 2 and, lastly, when rolling a 19 deals 3 points of damage. Have read the "dice reference" article at the wiki (which aided  me a lot) but, with my non-coding experience, have not found a way to express it on Roll20. About the issue i adressed before; A helpful user suggested me to use the rollable tables. But since I've had the advantage and disadvantage system, I need the d20 result as a Value while the rollable tables the result number is a Symbol (which, afaik, it's kinda hard to use advantage and disadvantage when you don't know what value is better or worse). :< Is it possible to attain this? Thanks in advance! PD. I'm not sure if this question should go to Specific Use Questions & Macros

You probably need a custom API script to handle something this complicated.  You could create 3 Rollable Tables, one for regular, one for advantage, and one for disadvantage, then weight the correctly based on the distribution of the dice. You can get the weights at anydice.com, just be aware that Rollable Tables use only the integer portion of the weight, so you man need to multiply all your weights by a scaling factor (day 1000, so 1.873 becomes 1873).