How can i customize a RadRumeric TextBox for mobile number validation. am using a RadRumeric TextBox for validating numbers. while using the same for mobile number validation it allows . how can i avoid this?
 <telerik:RadNumericTextBox ID="txtphone" Skin="WebBlue" runat="server" ValidationGroup="contact" Width="90%" MaxLength="32" NumberFormat-DecimalDigits="0">
           <NumberFormat DecimalDigits="0" DecimalSeparator ="."/>
 </telerik:RadNumericTextBox>
 <span class="warning">*</span><br />
 <asp:RequiredFieldValidator ID="RequiredFieldValidator25" runat="server" ControlToValidate="txtphone" CssClass="warning" ErrorMessage="Enter contact no." ValidationGroup="contact"></asp:RequiredFieldValidator>
when i give DecimalSeparator ="" will throws error
 
    