Open paypal comfirmation in a pop up then return url

How I have the pay flow setup is this..

In Facebook iFrame: Cart -> Shipping -> Confirm Order with Paypal -> Opens new Tab/Window

In that new Tab/Window: Paypal Login Page -> Confirm Paypal Payment -> Return (Redirect) Page is the raw url of the shop displaying this:

Thank you for your order! We appreciate your business, and please come back often to check out our new products.
Your PayPal payment for this order totaling $1.15 is complete. The PayPal transaction number is 70xxxxxxxxxx5D.
You may track the latest status of your order(s) here:
http://customtabs.co.nz/defaulttheme/store/order-status/6xxxxxxxxxx72/

Is there any way I can have the return page be sent back to the iframe? i guess it could be done with target=_parent ?

Would having the Paypal Login screen in a popup (instead of target=_blank).

Whats the url paypal uses as a redirect? and where can i find it in the core code?

and do you have any ideas?

Ben