HttpClient response (text/html) to Iframe

HttpClient response (text/html) to Iframe

I need an idea to solve this problem:
1) I have a Portlet that submit a form on external url (outside the
portal). The submit was provided with HttpClient and httpPost. 2) The
result is a html page. (obviously)
Now..
I need to put this content into an iframe (and use it after...) The URI
that I used in httpPost, I cannot use it inside the iframe src attribute,
because the page would be reloaded with loosing all previous information.
Now.. How can I do this?
Thanks in advance