Resolving a dynamic html form in C#

I am making an AutoCad plug-in which is basically a dll loaded by the main application. I need to communicate some data with a third party web service by sending them some data and receiving back some results. I am preparing the data and use httpClient.PostAsync() to send my data to the service.
However their service is more web oriented and the response to data being sent is an html form that runs javascript to show a progress bar and then redirects to a page with results. This page can later be used to recieve additional data with GET requests.

Question is:
How to get the result page for further communication?
Is using a WebBrowser to display html content and run javascript a viable option in this situation?

If possible I would like to avoid using unnecessary forms and resolve this without creating a WebBrowser form.

Also if there are better approaches to this I'd be glad to hear them.