JavaScript - AJAX Enabled WCF Service Function To Redirect To A New Window?

Scenario : I am going to access external web service [ExternalWS] using AJAX. So obviously, need to create local proxy service [LocalProxyWS] first, which in turn will access the external web service. Now, the external service webmethod [Process] basically redirects the current page on our site to their site, does some work and then return back to our site.

What I want : I want that when the user clicks the button ('Process') on our site, it should open a new window and then starts executing the request on the new window, so that I can have the page on my website to be displayed permanently (which will poll a request every 15 seconds to the external service (via local proxy) for the status).

Local Proxy service which calls external service is as follows..

[ServiceContract(Namespace = "LocalProxy")]
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class LocalProxyToExternalService
{
[OperationContract]
public void InitiateTransaction(string amount)

Basically, I am opening a new window from the button click and then want to process the new request in that new window, so that I can show the status to the user from the current page on my website So far, it opens the new window, but doesn't transfer the request on to that, but I get an error message in firebug as follows...