Implentation of Enroute and Scheduled APIs using XMLHTTP

Has anyone successfully implemented calls to Enroute and Scheduled using pure XMLHTTP directly from an SHTML page?

Here’s a sample of one of the many variations I’ve tried, but all I can seem to get is a documentation page, which leads me to believe it’s likely nothing more than a syntax or structure error.

For the record, I’m sure I am authenticating properly because if I change my username or key, then I receive an error.

Thanks in advance for any assistance provided.

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  xmlhttp.onreadystatechange=state_Change;
  xmlhttp.open("PUT",url,true,"**MASKED**","**Masked KEY**");
  xmlhttp.setRequestHeader("Content-Type","text/xml");
  xmlhttp.send("<?xml version='1.0' encoding='UTF-8'?>

<SOAP-ENV:Envelope xmlns:SOAP-ENV='http://schemas.xmlsoap.org/soap/envelope/' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xmlns:xsd='http://www.w3.org/2001/XMLSchema' SOAP-ENV:encodingStyle='http://schemas.xmlsoap.org/soap/encoding/'><SOAP-ENV:Body><ns1:Scheduled xmlns:ns1='Scheduled'><airport xsi:type='xsd:string'>KDTS</airport><howMany xsi:type='xsd:integer'>15</howMany><offset xsi:type='xsd:integer'>0</offset><filter></filter></ns1:Scheduled></SOAP-ENV:Body></SOAP-ENV:Envelope>");