function getData()
{
    var xhr;

    try {xhr = new ActiveXObject('Msxml2.XMLHTTP'); }
    catch(e)
    {
        try {xhr = new ActiveXObject('Microsoft.XMLHTTP'); }
        catch(e2)
        {
            try {xhr = new XMLHttpRequest(); }
            catch(e3) {xhr = false; }
        }
    }

    xhr.onreadystatechange = function()
    {
        if (xhr.readyState == 4)
        {
            if (xhr.status == 200) {
                document.exchange.result.value = xhr.responseText;
            } else {
                document.exchange.result.value = xhr.status;
            }
        }
    };

    var request_url = "data.php?from_alias=" + document.exchange.from.value + "&to_alias=" + document.exchange.to.value + "&amount=" + document.exchange.amount.value;

    xhr.open("GET", request_url, true);
    xhr.send(null);
}