How to popup a window in paymentprocessor "PostProcessPayment"???

Im developing a new payment method.
But i need to show a window (like popup) of a pure html (i got a string with the html) after the method "PostProcessPayment".
I already tried everything i found out, but nothing seems to works, tried to write javascript with "_httpContext.Response.Write" but it ignores it.
I don't know what more can I try.
If someone can help me plz.

Thanks in advanced.
Caio Moreno

I think the best you can do is a Response.Redirect. This way is you wont have any problems.

After the CheckoutController calls the PostProcessPayments, it immediately redirects to CheckoutComplete (or OrderDetails) view. So anything you write, will be lost.

A transfer can give you lots of troubles.

To integrate with Pagamento Digital, i just redirect to a view inside the plugin, that redirects the user to the gateway, because they receive data from Post only.

The thing is that I need to pop-up, its a "Boleto" html.
But anyway, i did it the worst way (i think) i changed the view of the Checkout complete, to add a button, that shows the pop-up.
It worked, but not the best pratice.

Thnks anyway