Sending data in XML format to Asp.Net from CS3

I need to send SQL statements to Asp.Net2 page from Action script 3.0 and i successed in doing that(thx to me OJM) but i need to secure my data and i need to send it in an XML format and recieve the results in an XML format and my problem now is how to send the data in an XML format where when i write the tags of the XML and send it in the URL variables it refuses and reports an error opening URL and when isend the SQL statements not in XML format it accepts it and recieved in the Asp page and i parse it and then return the result and i got it from the CS3 but my problem now that i need to send the data in an XML format can any one help me and tell me how write data in an XML with it’s tag and send it???