If you haven't tried the CRM 2011 SOAP Request Formatter yet, you should. It allows you to take a captured SOAP envelope and use it to generate and format a jscript web service call for you with very little effort.
The link to the original blog post that explains it's function and use here: http://mileyja.blogspot.com/2011/03/crm-2011-jscript-soap-request-formatter.html
The Microsoft Dynamics CRM 2011 SOAP Request Formatter tool has been updated to allow you to choose if you want your requests formatted as synchronous or asynchronous, where previously only asynchronous was supported.
You can download the latest version of the tool here: http://crm2011soap.codeplex.com/
I hope this helps!