I can't set Shipping Calculations for a Buy now Button - there's no option in my profile?

[Mtgs]

Hi. I have a UK Payments Standard. I want to set up buy now buttons for two products and set different postage prices for UK, Europe and USA.

I can't find anywhere to ad shipping calculations in :

Account Settings>Postage and Packing>Postage Calculations.

There is nowhere to ad international options.

Am I missing something?

Thanks, M