window.onload = InitPage;

function InitPage() {

    document.getElementById("ctl00_ContentPlaceHolder_btnFinish").onclick = btnFinish_Click;
    var btnFinish = document.getElementById("ctl00_ContentPlaceHolder_btnFinish");
    btnFinish.style.visibility = 'visible';
}

function btnFinish_Click() {

    var btnFinish = document.getElementById("ctl00_ContentPlaceHolder_btnFinish");
    btnFinish.style.visibility = 'hidden';

    return true;
}