cURL code for a single form

I need an "app" or web script written to which I can send values via POST or GET... that would then use these values to fill in a two-step form/URL that I do not control. When I say two-step, I mean the form takes a single value via POST or GET then refreshes itself to expose many more form fields. I do not need all of the fields auto-filled... just the primary ones near the top. So I would send the values to the "processor" page sitting on my server... which would then request the form and fill in the one field, wait for the refresh, then fill in many of the other fields. It would NOT submit the form, as the user would need to edit some of the fields not auto-filled. I assume the best way to do this is with PHP cURL. If there is a better way, I'm open to it. iconsult