Change Kendo Column with DDL

HTML

<script src="http://cdn.kendostatic.com/2012.2.710/js/kendo.all.min.js"></script>
<link rel="stylesheet" href="http://cdn.kendostatic.com/2012.2.710/styles/kendo.blueopal.min.css">
<link rel="stylesheet" href="http://cdn.kendostatic.com/2012.2.710/styles/kendo.common.min.css">
<select id="firstColoumnChoice">
    <option>Serial Number</option>
    <option>First Name</option>
    <option>Last Name</option>
</select>
<br />
<br />
<div id="columnChangingGrid"></div>

JavaScript

var serialNumbers = [123, 234, 534, 456, 765, 867, 890],
    firstNames = ["Nancy", "Andrew", "Janet", "Margaret", "Steven", "Michael", "Robert", "Laura", "Anne", "Nige"],
    lastNames = ["Davolio", "Fuller", "Leverling", "Peacock", "Buchanan", "Suyama", "King", "Callahan", "Dodsworth", "White"],
    statuses = ["Unknown", "Inactive", "Active"],
    birthDates = [new Date("1948/12/08"), new Date("1952/02/19"), new Date("1963/08/30"), new Date("1937/09/19"), new Date("1955/03/04"), new Date("1963/07/02"), new Date("1960/05/29"), new Date("1958/01/09"), new Date("1966/01/27"), new Date("1966/03/27")];

function createRandomData(count) {
    var data = [],
        now = new Date();
    for (i = 0; i < count; i++) {
        var serialNumber = serialNumbers[Math.floor(Math.random() * serialNumbers.length)],
            firstName = firstNames[Math.floor(Math.random() * firstNames.length)],
            lastName = lastNames[Math.floor(Math.random() * lastNames.length)],
            status = statuses[Math.floor(Math.random() * statuses.length)],
            birthDate = birthDates[Math.floor(Math.random() * birthDates.length)];

        data.push({
            SerialNumber: serialNumber,
            FirstName: firstName,
            LastName: lastName,
            Status: status,
            DOB: birthDate
        });
    }
    return data;
}

var columnDefinitions = [
    {
    field: "SerialNumber",
    title: "Serial Number"},
{
    field: "FirstName",
    title: "First Name",
    hidden: true},
{
    field: "LastName",
    title: "Last Name",
    hidden: true},
{
    field: "Status",
    title: "Status"},
{
    field: "DOB",
    title: "DOB",
    template: "#= kendo.toString(DOB,'MM/dd/yyyy') #"}];

var gridDataSource = new kendo.data.DataSource({
    data: createRandomData(50),
    pageSize: 10,
    schema: {
        model: {
            fields: {
                SerialNumber: {
                    type: "number"
                },
                FirstName: {
      ...