WebBrowser - posting form data

I want to scrape pages for current grocery store advertisements.

I know how to do everything except one piece, posting form data back
automatically with the WebBrowser.

For instance if you go to www.kroger.com, I would like to automatically
enter my zip code and then auto click the "GO" button. The zip code is part
of a HTML form
<form method="post"
<input name="zip"

Is there a way to do this?

Thanks,
Dave