UpdateProgress centrato dinamicamente

<script language="JavaScript" type="text/javascript">

        function adjustDivs() {           

            interno = document.getElementById('divCalcolaInterno');

            esterno = document.getElementById('divCalcola');

            dfs = interno.style;

           

            dfs.left = (esterno.innerWidth - interno.offsetWidth) / 2;

        }

        window.onload = adjustDivs;

        window.onresize = adjustDivs;

        window.onscroll = adjustDivs;

<script>

<asp:UpdatePanel ID="updXXX" runat="server">

<ContentTemplate>

       […]

<ContentTemplate>

<asp:UpdatePanel>

<asp:UpdateProgress ID="updprogXXX" runat="server" AssociatedUpdatePanelID="updXXX" DisplayAfter="150">

<ProgressTemplate>

             <div id="divCalcola" align="center" style="top: 200px; position: absolute; top:0; bottom:0; right:0; left:0;background-color:rgba(0,0,0,0.5)">

                    <div id="divCalcolaInterno" align="center" style="border: solid 1px #000000; background: #FFFFFF;padding: 5px; width: 320px; height: 50px;margin-top:300px">

                        <asp:Label runat="server" ID="lblLoading2" Text="Calcolo del fatturato in corso..."><asp:Label>

                        <asp:Image ID="imgLoading2" runat="server" ImageAlign="left" SkinID="imgLoadingBar" /><br /><br />

                        <asp:Label runat="server" ID="lblLoadingInfo" Text="Questa operazione potrebbe durare diversi minuti" Font-Size="X-Small" >asp:Label>

                    <div>

                <div>               

        <ProgressTemplate>

<asp:UpdateProgress>