Numeric validation not working in input type text when I add them dynamically

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C#5.0

I add these text boxes dynamiccaly by using javascript. I want these text boxes has to take only numeric values, but validation javascript not working for them..

Here is my Design.. I display the text box inside a modal then increment them one by one.

<div class="modal-content">
                           <div class="modal-header">
                               <button type="button" class="close" data-dismiss="modal" aria-hidden="true">&times;</button>
                               <h4 class="modal-title">ADD PHONE NUMBERS</h4>
                           </div>
                           <div class="modal-body">
                               <p>Please  add  alternate phone numbers:</p>

                               <div class="phoneDiv">

                                   <div class="phoneRow">
                                       <input class="form-control input-sm" id="setPhone0" maxlength="14" onkeypress="return IsNumeric(event);" ondrop="return false;" onpaste="return false;" />
                                       <span class="removeThis">X</span>
                                   </div>

                               </div>
                               <button class="btn btn-link showLinkbutton" type="button"><i class="glyphicon glyphicon-plus-sign"></i>Add More</button>


                               <div class="clear"></div>

                           </div>
                           <div class="modal-footer text-center">

                               <button type="button" class="btn btn-info" id="submitPhoneNumbers">Save changes</button>
                               <button type="button" id="btnClose" class="btn btn-info" data-dismiss="modal" aria-hidden="true">Close</button>
                           </div>
                       </div>

Thanks & regards
Bigyan Sahoo

What I have tried:

javascript validation code

<script type="text/javascript">
function IsNumeric(e) {
var keyCode = e.which ? e.which : e.keyCode
var ret = ((keyCode >= 48 && keyCode <= 57) || specialKeys.indexOf(keyCode) != -1);
return ret;
}

</script>