how to find control in item template of multicolumn radcombobox in javascript?

See more:

ASP.NET

Javascript

Telerik

Dear Sir/Madam,
how to find control in item template of multicolumn radcombobox in javascript?
For Example,
i have radnumerictextbox in the radcombo

<telerik:RadNumericTextBox ID="Ins_unitprice" runat="server" MaxLength="10"  autocomplete="off" NumberFormat-DecimalDigits="4"

ShowSpinButtons="True" Width="60px" Height="18px" Skin="Web20" OnChange="return calculate_item_price();" >
</telerik:RadNumericTextBox>

I have to get this textbox id in JavaScript

Thanks in Advance