Create Button in CRM Form without a Field using Javascript

///http://missdynamicscrm.blogspot.in/2015/06/create-button-in-crm-form-javascript.html

function btncal() {
    createButton(id, defaultText, intWidth, onClickEventFunctionName);
}

function createButton(id, defaultText, intWidth, onClickEventFunctionName) {
    debugger;
    var btn = document.createElement("BUTTON");

    // Create a <button> element, you can also use input,but need to set type to button
    var t = document.createTextNode(defaultText);
    btn.appendChild(t);
    btn.className = "ms-crm-Button";
    btn.id = id;

    if (intWidth != null) {
        btn.style.width = intWidth + "px";
    }
    else {
        //defaulted width
        btn.style.width = "100%";
    }

    btn.onmouseover = onCRMBtnMouseHover;
    btn.onmouseout = onCRMBtnMouseOut;

    btn.onclick = onClickEventFunctionName;

    return btn;
}

//use this for creating a button with hovering style like CRM has
function onCRMBtnMouseHover() {

    Mscrm.ButtonUtils.hoverOn(this);
}

function onCRMBtnMouseOut() {

    Mscrm.ButtonUtils.hoverOff(this)
}
function createButtonCalculate() {
    //debugger;
    var btnTemplate = createButton("btnCalculateCourseFeePerHour", "Calculate", 100, btnCalculate_onClick);

    //put this code if you want to insert the button just after a field,
    var insertAfterField = parent.document.getElementById('new_abcal');
    insertAfterField.parentElement.insertBefore(btnTemplate, insertAfterField.nextSibling);

    //if you want to put after a grid, section, or another element it is possible also/
    //remember it is using DOM method
    //if you want to put before an element, just use this (without nextSibling
    //insertAfterField.parentElement.insertBefore(btnTemplate, insertAfterField);

}
function btnCalculate_onClick() {
    //put your logic here
    var a = Xrm.Page.getAttribute("new_a").getValue();
    var b = Xrm.Page.getAttribute("new_b").getValue();
    var ab = a + b;
    Xrm.Page.getAttribute("new_abcal").setValue(ab);
    alert("clicked!");
}