How to set Numeric Format and the number of decimals to a Field with Javascript?

Thanks to you guys, I tried my best, but I did not make it function 😞

My Javascript code is in a button, each time the user clicks on it, it adds a new row of fields, but the fields that are manually setted up as Numeric with 3 decimals since row number two(2) it is not functioning, it is without any format.

This is my JS code in the button:

var totalCount = 1;
var totalCount2 = 0;
for (var fieldNumber = 0; fieldNumber < numFields; fieldNumber ++)
{
if(getNthFieldName(fieldNumber).startsWith("CONTAINER_CONTAINER_NRO")){
totalCount++;
totalCount2++;
}
}

var offset = this.getOffset();
var fieldNames = this.getFieldNames();
for (var i = 0; i < fieldNames.length; i++)
{
var fieldName = fieldNames[i] + "_";
var rectLast = this.getField("CONTAINER_" + fieldName +totalCount2 ).rect;

var newField = this.addField("CONTAINER_" + fieldName + totalCount, "text", 1, [rectLast[0],rectLast[1] - offset ,rectLast[2],rectLast[3]-offset ]);

if(fieldName === "QUANTITY_VOL_"){
var customFormat = AFNumber_Format(3, 0, 0, 0, "", false);
var myField = this.getField(fieldName );
myField.setFormat(customFormat);
}
}

this.getField("REMOVE_CONTAINER").display = display.visible;

if(totalCount >= this.getMaxQuantityFields()){
this.getField("ADD_CONTAINER").readonly = true;
}

Inside the body of the 'if' it is where I want place my code that will give a Numeric Format and set up to 3 decimals to whichever value the user input into the field, the name of the field is: "QUANTITY_VOL_")

I do not have idea what I am doing wrong.

There isn't a direct command to do it. You would need to use the setAction method to specify the Format and Keystroke scripts for the field, and either write your own code that does it, or have knowledge of the undocumented functions that Acrobat uses to apply those settings.