Customers click a join button using a form (with 'form action="[url removed, login to view]" method="post" target="_blank"', 'input type=hidden name=.....value="........"' etc) ;
I want that, instead of being immediately led to hwere they are expected ([url removed, login to view]), they first go to another, intermediate page (located in members area of another site) where they will immediately redirected to [url removed, login to view]
The reason is that before paying for site A, they must also be members of site B.
The intermediary page verifies that.
I know how to make redirections with meta tag content rtefresh, but not with a form.
Of course I could place the form in members area of site B, and just put a link to that, on site A, but this makes an additional step before people pay...