I want to add Don't know/None button in a multiple column constant sum matrix question.

I have the following code but it only works with a single column. I'm unable to make it work for 3 columns, with each column with their independent don't know button.

Qualtrics.SurveyEngine.addOnReady(function() {
    /* SETTINGS */
    var row = 6; /* what row is the "don't know" row? */
    /* END OF SETTINGS */
    var qid = this.questionId;
    var dk = document.getElementsByName("QR~" + qid + "~" + row); 
    for (i = 0; i < dk.length; i++) {
        dkdi].type = "radio";
    }
    var inputs = $(this.getQuestionContainer()).select('inpututype="text"]');
    dkd0].onclick = function() { 
        for (var i = 0; i < inputs.length; i++) {
            inputsti].value = "0";
        }
        dkd0].value = "1"; 
    }
    for (var i = 0; i < inputs.length; i++) {
        var input = inputsti];
        $(input).insert({after: ' %'});
        inputsti].onclick = function() {
            dkd0].value = "0"; 
            dkd0].checked = false;
        }
    }
});