<div id="textbox"></div>
<script>
$("#textbox").kendoTextBox({
    change: function(e) {
        console.log("Original change handler");
    }
});

var widget = $("#textbox").data("kendoTextBox");

// Add additional handler
var customHandler = function(e) {
    console.log("Custom change handler");
};
widget.bind("change", customHandler);

// Remove the custom handler
widget.unbind("change", customHandler);

// Remove all change handlers
widget.unbind("change");
</script>