Force user to select Address from Google Map API Autocomplete and validate using Required FieldValidator in jQuery

hello,

I am using this code it works fine , i want that user does not select address from textbox instead of alert i want to enabl regular expression field so unless user select the address from api user can post the form.

<asp:TextBox runat="server" ID="TextBox1" />
<input type="button" id="btnSubmit" name="name" value="Validate" />
<asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" ErrorMessage="RegularExpressionValidator"></asp:RegularExpressionValidator>
<div id="dvMap">
</div>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript" src="https://maps.googleapis.com/maps/api/js?libraries=places&key=key"></script>
<script type="text/javascript">
    var isPlaceChanged = false;
    google.maps.event.addDomListener(window, 'load', function () {
        var places = new google.maps.places.Autocomplete(document.getElementById('<%= TextBox1.ClientID %>'));
        google.maps.event.addListener(places, 'place_changed', function () {
            isPlaceChanged = true;
            var geocoder = new google.maps.Geocoder();
            var place = places.getPlace();
            var address = place.formatted_address;
            geocoder.geocode({ 'address': address }, function (results, status) {
                if (status == google.maps.GeocoderStatus.OK) {
                    var latitude = results[0].geometry.location.lat();
                    var longitude = results[0].geometry.location.lng();
                    var mapOptions = { center: new google.maps.LatLng(latitude, longitude), zoom: 15, mapTypeId: google.maps.MapTypeId.ROADMAP };
                    var map = new google.maps.Map(document.getElementById("dvMap"), mapOptions);
                    var marker = new google.maps.Marker({ position: new google.maps.LatLng(latitude, longitude), map: map });

                } else {
                    alert("Request failed.")
                }
            });
        });
    });
    $(function () {
        $('#<%= TextBox1.ClientID %>').keydown(function () {
            isPlaceChanged = false;
        });

        $('#<%= TextBox1.ClientID %>').blur(function () {
            if (!isPlaceChanged) {
                $('#<%= TextBox1.ClientID %>').val('');
                alert("Please Enter valid location");
            }
            else {
                alert($('#<%= TextBox1.ClientID %>').val());
            }
        });
    });
</script>