how to cal javascript method in server side button control?

function calcRoute() {
            var start = document.getElementById('start').value;
            var end = document.getElementById('end').value;


            var request = {
                origin: start,
                destination: end,

                travelMode: google.maps.TravelMode.DRIVING
            };
            directionsService.route(request, function(response, status) {
                if (status == google.maps.DirectionsStatus.OK) {
                    directionsDisplay.setDirections(response);
                    var route = response.routes[0];
                    var summaryPanel = document.getElementById('directions_panel');
                    summaryPanel.innerHTML = '';
                    // For each route, display summary information.
                    for (var i = 0; i < route.legs.length; i++) {
                        var routeSegment = i + 1;
                        summaryPanel.innerHTML += '<b>Route Segment: ' + routeSegment + '</b><br>';
                          summaryPanel.innerHTML += route.legs[i].start_address + ' to ';
                        summaryPanel.innerHTML += route.legs[i].end_address + '<br>';
                        summaryPanel.innerHTML += route.legs[i].distance.text + '<br><br>';
                    }
                }


            });
        }

        google.maps.event.addDomListener(window, 'load', initialize);

my button event is not fired...i want to shows the get directions using two dropdown list controls using server side controls but my button event is not fired ...wht i do?


     <asp:Button ID="btnsubmit" runat="server" OnClientClick="return calcRoute();" Text="Submit" />