First of all, I believe that this tip I’m writing on this post is not necessary for 99.99% of users and, actually, I don’t recommend using it. I’m writing this for the 0.01% of you, so you can ignore it if not necessary.
This is what the author says. ;-)
But as long as Contact Form has no Paypal connection, it's usefull to make training courses' order forms.
Name, email, phone, etc.
redirect to page 2
Paypal training cart. Pay here !
(WordPress Simple Paypal Shopping Cart Plugin. Very nice)
Paypal redirect to page 3.
Confirmation and thank you for your order.
May be useful to someone more.