Set Max number of files to be uploaded in ASP.Net Multiple FileUpload control

<input id="FileUpload1" onchange="Validate()" type="file" multiple="multiple" />
<script type="text/javascript">
    function Validate() {
        var fileCount = document.getElementById("FileUpload1").files.length;
        if (fileCount > 4) {
            alert("max 3 images allowed.");
            document.getElementById("FileUpload1").value = null;
        }
    }
</script>