How To Simulate HTTP POST Using Headers?

This is the scenario: I am making a wizard composed of several steps, each
step being a form with the post method. The first steps may be completed
whether the user is logged on to the website or not. But from a certain step
on the user must be logged on to complete the wizard. What I do is post the
data gathered so far to the logon page; the logon page is essentially an ASP
page with an HTML logon form that posts to itself. Once the user logs on he
is taken again to the wizard, to the step where he left off.

Right now I am using the HTML form / approach on the
logon page: after the user is authenticated, the asp page builds a form with
the "saved" data, pointing to the next step of the wizard, and uses the
onLoad event of the body tag to submit the form. And this does what I
intended.

But I believe there must be a more elegant way to do this, and I suspect it
involves setting headers directly using Response.AddHeader but I don't know
how to do it. Am I right? If so, how to do it?