Programmatically calling HTTP Post using Indy's TIDHttp


I am using Indy's TIDHttp to programatically submit Http Get and Post
requests to IntraWeb Application created in App-Mode ISAPI.
The Get is working but I need some help with getting Post to work.

Something really simple.
I have an IW Form with a button and an Edit box.
When the button is clicked the text in the EditBox changes to 'Hello'

Using TIdHttp I call the Post method.
But what do I need to pass to Post to get the response back.

Right now I am getting "text/html" returned back but it does not have
the string 'Hello' in it.
Somewhere in the 'text/html' returned back I expect to see
  name="IWEDIT1" value="Hello"

However, when I don't get back the string "Hello".

Code is same as HttpClient demo in Indy8 being used in Indy9 (with some
comments to get it compiled).

What do I need to pass as arguments to TIDHttp's Post method to get it
submit the form, fire the event and return back the string in the Edit box?