var message="Sorry, the source is locked.";
    function clickIE4() {
        if (event.button==2) {
            alert(message);
            return false;
        }
    }
    function clickNS4(e) {
        if (document.layers||document.getElementById&&!document.all) {
            if (e.which==2||e.which==3) {
                alert(message);
                return false;
            }
        }
    }
    if (document.layers) {
        document.captureEvents(Event.MOUSEDOWN);
        document.onmousedown=clickNS4;
    } else if (document.all&&!document.getElementById) {
        document.onmousedown=clickIE4;
    }
    document.oncontextmenu=new Function("alert(message);return false")