if total[nilai] < target , tambah textbox baru, else all textbox readonly

Tolong bantu, untuk masalah pada saat onkeypress textbox nilai maka menjumlahkan semua nilai jika total[nilai] < target

maka otomatis add new textbox dan jika total[nilai] >= target maka semua textbox readonly

<label> Target: </label>
<input id="target" type="text" name="target">

<br><br>

<div id="afters">
<label>Nilai:</label>
<input  id="nilai" type="text" name="nilai[]">
</div>
<br>

<br>
<p id="demo"></p>

<script>
document.getElementById("nilai").onkeyup = function() {myFunction()};

function myFunction(){
    var target = parseInt(document.getElementById("target").value) ;
    var nilai = parseInt(document.getElementById("nilai").value) ;
if(nilai < target){
document.getElementById("demo").innerHTML = "<b style='color:red;'>" + "False" +"</b>";
var input = document.createElement("input");
                input.type = "text";
input.name = "nilai[]";
input.id ="nilai";
var br = document.createElement("br");

             document.getElementById("afters").after(input,input.appendChild(br));

}else{
document.getElementById("demo").innerHTML = "<b style='color:Green;'>" + "True" +"</b>";
}}
</script>