Yes, you can modify the simple shopping cart to specify a different page style.
Once the Page Style is set in PayPal all that is necessary to activate it (on the fly) as it passes to Paypal, is one line of HTML code.
<input type="hidden" name="page_style" value="style name">
where “style name” is the name of the Page Style page you set in Paypal.
If you didn’t know your way around HTML and PHP then here is what you need to do…
1. Open the “wp_shopping_cart.php” file and search for the following line:
<input type="hidden" name="cmd" value="_cart" />
2. Now, add the line that adds a custom page style like the follwoing:
<input type="hidden" name="cmd" value="_cart" /><input type="hidden" name="page_style" value="style name">
3. Save and upload the modified file and you are done.
Now when someone clicks the checkout button and goes to PayPal they will see the customer checkout page that you have specified.