[monolithed]

<script type="text/javascript">
window.onload = function() {
    var forma = document.forma.elements;
    forma[3].onclick = function() {
        var val = function(i) {
            return parseFloat(forma[i].value);
        };
        forma[2].value = val(0) + val(1);
        return false;
    };
};
</script>
<form name="forma">
    <input type="text" value="" /> +
    <input type="text" value="" /> =
    <input type="text" value="" readonly="readonly" />
    <input type="submit" value="click" />
</form>