function validate() {
    if((document.getElementById("txtBedrijf").value.length != 0) &&
        (document.getElementById("txtNaam").value.length != 0) &&
        (document.getElementById("txtFunctie").value.length != 0) &&
        (document.getElementById("txtEmail").value.length != 0) &&
        (document.getElementById("txtTelefoon").value.length != 0)) {
        document.getElementById("cmdDownload").disabled = false;
        document.getElementById("txtDownload").innerText = 'U kunt beginnen met downloaden';
        return true;
    } else {
        document.getElementById("cmdDownload").disabled = true;
        document.getElementById("txtDownload").visibility = 'Niet alle gegevens zijn ingevoerd';
        return false;
    }
}
function startdownload() {
        document.getElementById("cmdDownload").disabled = true;
        document.getElementById("txtDownload").visibility = 'Een ogenblik gedult a.u.b.';
}