Dynamically load and insert external data into a php page

I have a PHP shopping cart (zen-cart) and I have problems with the shipping page taking way too long to display.  This is because the shipping provider's server is too slow... in other words, beyond my control.

I just want to be able to let the customer know what's going on.

How it works now is the shopping cart waits for the entire page to load, including all external data, before displaying ANYTHING.  I'd like to modify that.  I want the page to load without waiting for the external data, and just show something like "retrieving shipping rates... please wait" until that data finally arrives, then display it to the user.  The "continue" button won't be available until the data is complete, so there has to be some way of knowing when the data has arrived.

I don't even know where to begin.  My first problem is how do I get the php cart to "ignore" the fact the data isn't all there yet.  My next problem is how do I continue to retrieve that data anyway (sort of like multi-threading).  My final problem is how do I then replace the "please wait" with the actual data without reloading the page.

I hope this is an appropriate place to ask.

I think the best way to do this is to assign a relatively low amount of points and just ask that you give me some tips on what to research to get me started.  Then, when I have more specific questions, I can better ask them.  Thanks.Start Free Trial