Pop up blocker blocks my shopping cart

I’m integrating a pay-pal shopping cart onto a web site I’m designing. I spent a lot of time trying to get it to work, then realized there was no problem with the code. The shopping cart appears as a window on the website, and it was being blocked by the pop-up blocker. I was able to fix the problem easily by disabling the blocker for this domain, but I don’t think a lot of customers would think to do the same. I could put a message on the web page saying something like ‘hey, you, the shopping cart will not work unless you disable the pop up blocker!’, but there must be a better way. Have any of you guys out there had the same problem, and if so, how did you deal with it?

Most popup blockers will allow the popup if the user holds the ‘shift’ key down. You could put some text beside the button to indicate that.

Just to make sure the obvious is covered, can you make the shopping cart not be a pop-up, and be integrated into the page?