Hi,

you can add an event handler to the ModalPopup showing event and set the focus with a javascript function. Add this script to your page:

<script type="text/javascript">
   
    Sys.Application.add_load(modalSetup);

    function SetFocusOnControl()
    {
        // set the focus with javascript, e.g.: window.getElementById("xyz").focus();
    }
    function modalSetup()
    {
        var modalPopup = $find('ModalDialogTest');             // <. this is the BehaviorID from the ModalPopupExtender
        modalPopup.add_showing(SetFocusOnControl);         
    }

</script>

Regards

Marc André