How to solve On change going into infinite loop?

 <telerik:RadDateTimePicker ID="rdtp_arrival" runat="server"></telerik:RadDateTimePicker>
 <telerik:RadDateTimePicker ID="rdtp_departure" runat="server" ClientEvents-OnDateSelected="cng_departure"></telerik:RadDateTimePicker>
<telerik:RadNumericTextBox ID="rnt_night" runat="server" Culture="en-US" DataType="System.Int32" DbValueFactor="1" LabelWidth="64px" MinValue="1" ShowSpinButtons="True" Width="100%" ClientEvents-OnValueChanged="inc_check">
    <NegativeStyle HorizontalAlign="Center" />
    <NumberFormat ZeroPattern="n"></NumberFormat>
    <DisabledStyle HorizontalAlign="Center" />
</telerik:RadNumericTextBox>

JS

function cng_departure() {
var datePicker11 = $find("<%= rdtp_arrival.ClientID %>");
var datePicker12 = $find("<%= rdtp_departure.ClientID %>");
var minutes = 1000 * 60;
var hours = minutes * 60;
var days = hours * 24;
var valueTbx = $find('<%=rnt_night.ClientID %>');
valueTbx.set_value(Math.ceil((datePicker12.get_selectedDate() - datePicker11.get_selectedDate()) / days));
}

function inc_check() {
     var datePicker1 = $find("<%= rdtp_arrival.ClientID %>");
     var datePicker2 = $find("<%= rdtp_departure.ClientID %>");
     var date = datePicker1.get_selectedDate();
     date.setDate(date.getDate() + parseInt($('#<%= rnt_night.ClientID %>').val()));
     datePicker2.set_selectedDate(date);
 }

When i increase night or change departure date it goes in a infinite loop which calls each other inc_check and cng_departure methods until site crashes. if i remove onchange event from any one control it works properly. what to do now?