HTM page manipulation

[C_ntua]

I want generally to get information about a web page. I manage to get the htm code and save it, in order to parse it. But the page (.aspx) has multiple pages that you can select by pressing selecting the page.

I know that if I select the page it will do

javascript:_doPostBack(something)

Can I do this programmatically? Like force it to execute the javascript function with the specific parameter I choose? Is there another way to make it load a page that you don't know the specific link?

[C_ntua]

Here is the javascript function

function __doPostBack(eventTarget, eventArgument) {
    if (!theForm.onsubmit || (theForm.onsubmit() != false)) {
        theForm.__EVENTTARGET.value = eventTarget;
        theForm.__EVENTARGUMENT.value = eventArgument;
        theForm.submit();
    }
}

There are two hidden fields __EVENTTARGET and __EVENTARGUMENT in the form.
I would want
1) to get those fields
2) change them accordingly
3) force the page to postBack

Can I do this with GET/POST methods from the HttpWebRequest? This is a whole new field from me

[C_ntua]

(why am I filling alone? :P)

Well, googling around didn't give me any answer. But I found an intersting class called
WebBrowser. It just lets you do whatever you want, simple as that.