是否可以使用Ajax来调用其他Ajax中的php脚本？

I have a checkbox that whenever it is checked it calls another php script using Ajax, now on the php script I got 3 text boxes with a button, and whenever the Button is pressed, Ajax will be preformed to call another php script. all of that are preformed in the same page!, it is just like this

PHP -> Ajax -> PHP -> Ajax -> PHP

Is it possible, or too much to process?!

my first Ajax is:

<script type = 'text/javascript'>
        function load(cb, pos)
        {
            if (cb.checked == false)
            {
                document.getElementById(pos).innerHTML="";
                return;
            }
            if (window.XMLHttpRequest)
                xmlhttp = new XMLHttpRequest();
            else
                xmlhttp = new ActiveXObject('Microsoft.XMLHTTP');

            xmlhttp.onreadystatechange = function()
            {
                if (xmlhttp.readyState == 4 && xmlhttp.status == 200)
                    document.getElementById(pos).innerHTML = xmlhttp.responseText;
            }

                xmlhttp.open('GET', "trying.inc.php?pass='true'", true);
                xmlhttp.send();
        }
    </script>

The second Ajax that is in "Tring.inc.php":

<script type = 'text/javascript'>
    function check()
    {
        if (window.XMLHttpRequest)
            xmlhttp = new XMLHttpRequest();
        else
            xmlhttp = new ActiveXObject('Microsoft.XMLHTTP');

        xmlhttp.onreadystatechange = function()
        {
            if (xmlhttp.readyState == 4 && xmlhttp.status == 200)
                document.getElementById('adiv').innerHTML = xmlhttp.responseText;
        }

        Parameters = "OldPass="+document.getElementById('OldPass').value+"&newPass="+document.getElementById('newPass').value+"&Confirm="+document.getElementById('ConfirmPass').value;

        xmlhttp.open('POST', 'Trying2.inc.php', true);
        xmlhttp.setRequestHeader ('Content-type', 'application/x-www-form-urlencoded');
        xmlhttp.send(Parameters);
    }
</script>

that calls "Trying2.inc.php".

now when I am at "trying.inc.php" page, Ajax works in calling "trying2.inc.php", but from the main page I can call "trying.inc.php" however, "trying.inc.php" can't call "trying2.inc.php", I hope it is clear because I don't know how to explain it more. If it is possible what can I do to achieve it, please support it with code. Im doing this for learning purposes please don't be harsh on me, Thanks in advance.

If you are using jquery, you could use bind/live on the elements newely added to the dom, thus you must be able to do this.