<telerik:RadDatePicker runat="server" ID="DateNeededDP">
<ClientEvents OnDateSelected="DateSelected" />
</telerik:RadDatePicker> 

<telerik:RadDatePicker runat="server" ID="EffDateDP" >
<ClientEvents OnDateSelected="DateSelected" />
</telerik:RadDatePicker>

<telerik:RadDatePicker runat="server" ID="EndDateDP">
<ClientEvents OnDateSelected="DateSelected" />
</telerik:RadDatePicker>

function DateSelected(sender, eventArgs) {

    formdirty();

    var node = sender.get_id().substr(sender.get_id().indexOf("_MainContent_") + 13);

    if (node == "EndDateDP") {

        var datePicker = $find("<%= EffDateDP.ClientID %>");

        var effdate = datePicker.get_selectedDate();

        var enddate = sender.get_selectedDate();

        if (enddate <= effdate) { 
                    eventArgs.set_cancel(true);

                    alert("End Date must be greater than Effective Date");

                }

        }

         if (node == "EffDateDP") {

        var datePicker = $find("<%= EndDateDP.ClientID %>");

        var enddate = datePicker.get_selectedDate();

        var effdate = sender.get_selectedDate();

        if (enddate <= effdate) { 
                    eventArgs.set_cancel(true);

                    alert("Effective Date must be less than End Date");

                }

        }

    if (node == "DateNeededDP") { 
        var Neededdate = sender.get_selectedDate();

        var today = new Date();

        if (Neededdate < today) {

                    eventArgs.set_cancel(true);

                    alert("Needed Date must be greater than Today");

                }

        }

}


The alerts fire correctly but it is not canceling the selected date.  And help would be great.