Confirm dialog with Yes No Button instead of OK and Cancel in ASP.Net

I need to display a message in button click with yes no button ..But pop up shows ok,cancel button.

 <script type = "text/javascript">
         function Confirm() {
             var confirm_value = document.createElement("INPUT");
             confirm_value.type = "hidden";
             confirm_value.name = "confirm_value";
             if (confirm("Are you sure, you want to Close BOM?")) {
                 confirm_value.value = "Yes";
             } else {
                 confirm_value.value = "No";
             }
             document.forms[0].appendChild(confirm_value);
         }
    </script>