appears aware cart code domains due hopes iframes item items purchase redirect sessions setup similar site sites software websites

As you may or may not know, we're using your cart software with two of our websites. One of our hopes of having both sites use the same cart is that people would be able to purchase an item from one site and another item from the other site in the same purchase. Unfortunately, this appears to not be possible, as when you go to the second site, the cart doesn't have the items that was in it before. I assume this may be due to sessions within the code
or something, but is there anyway around this, that you're aware of?
I realize we could just use iframes, or something similar, but I thought I might ask.

I am sorry but that's not possible as both the sites have different domains. If you can redirect one site to the other and setup the site there, that will work fine.