I would like to change the return page url for PayPal checkout.

CC's instruction says set return url in my PP profile to a page in my shop. PP says that an a url to override that can be passed when checkout is invoked.

I will have several shops using the same PP account. I will need to return to those shops from the same PP checkout.

I am using payments standard.

I am competent in html, jscript, and php. Point me to the right modules in my exported cart and I can do the tweaks.