I want a PayPal button in which the price of the article is fed to the button from a database table.

e.g. : The customer looks at a list of items and clicks on the one he wants. The price is taken from a database table. How do I "feed" this price to the PayPal button ?

I think it needs the PayPal API, but I can NOT find where to look for information.

Someone must have done this.