Direct unit purchase, bypassing shopping cart

With PayPal IPN (Website Payments Standard) the shopping cart total is transferred to the paypal page (in the top right) so that the user can see the amount due...

I'm eager to get a 'buy now' button that does this but for an individual product rather than the entire shopping cart contents (the button would be available in product info)...

I have been playing around with the PayPal Express Checkout for this as I thought it would be the best choice for this... the point of this is to provide an option for the user to buy the particular product that they are on without effecting their current shopping cart items..

can anyone push me in the right direction for this

_thanks