in my mind it seems more simple (but i guess i need to start coding it to realise :)
I know to store it in a session but that session wouldnt be created until the customer selects the appropriate option on the checkout page and then clicks the button that takes them to paypal. so the only way i can think for it to be displayed on the checkout page is to have the options for delivery charges on the cart page which is soemthing i dont want to do as it looks a bit odd. since i was using checkout page to do all the address type stuff :)