using radio in ASP.NET treeview instead of checkboxes

<script type="text/javascript">

    function MakeRadio() {

        var tv = document.getElementById("<%= TV.ClientID %>");

        var chkArray = tv.getElementsByTagName("input");

        for (i = 0; i <= chkArray.length - 1; i++) {

            if (chkArray[i].type == 'checkbox') {

                chkArray[i].type = 'radio';

            }

        }

    }

    window.onload = MakeRadio;

    function OnTreeClick(evt) {

        var src = window.event != window.undefined ? window.event.srcElement : evt.target;

        var isChkBoxClick = (src.tagName.toLowerCase() == "input" && src.type == "radio");

        if (isChkBoxClick) {

            SelectOne(src.id);

        }

    }

    function SelectOne(objId) {

        var tv = document.getElementById("<%= TV.ClientID %>");

        var chkArray = tv.getElementsByTagName("input");

        for (i = 0; i <= chkArray.length - 1; i++) {

            if (chkArray[i].type == 'radio') {

                if (chkArray[i].id != objId) {

                    chkArray[i].checked = false;

                }

            }

        }

    }

</script>

<asp:TreeView ID="TV" runat="server"></asp:TreeView>

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

                TV.Attributes.Add("onclick", "OnTreeClick(event)")

End Sub