Problem with an Application like Google Ads

[EL FRASKA]

Hi, im doing an application that is implementated like Google Ad. For
Example, this is the script that i want for my clients need in your
apge to use the service....
(This is an example, the script is dynamically generated)

<script type="text/javascript"><!--
_id = "XX34DXERF";
_textcolour = "#0099ff";
_bgcolour = "#ffffff";
_titlecolour = "#000000";
_horizontal=1;
//--></script>
<script type="text/javascript"
src="http://www.something.com/searchb.js">
</script>

Later in searchb.js i need to send the parameters (_id = "XX34DXERF";
_textcolour =..... ) to my server where is processed. And finally i
include a php file with this parameters sended by post...

In http://something.com/searchb.js im doing an AJAX
myConn.connect("http://www.something.com/searchbox.php", "POST",
"csur_textcolour= " + csur_textcolour +
"&csur_bgcolour= " + csur_bgcolour + "&csur_titlecolour= " +
csur_titlecolour + "&csur_horizontal= " + csur_horizontal + "&test= 1",
fnWhenDone);

THE PROBLEM: If I use the first code autogenerated i na page of my
server its works, but if im use it in a external server the page is
showed blank. I think my problem is that im doing it with ajax and i
cant use XMLHTTP.open cross-domain to send parameters to my php. I was
looking to solve the problem but i dont find any solution to
cross-domain scripting with XMLHTTP. But the Javascript console dont
showed any error¿?

Any solution for my problem o another way to do this application.

Thanks