A buddy of mine is giving out free copies of his software at the moment to anyone who gives money to Haiti.  He is doing it on the honor system.  I think that is likely to be sufficient, depending on who your customer is.<p>Failing that, see the Paypal documentation about Return URLs.  The one set up with the button has priority over the global one specified per Paypal account.  Thus, if you know the email address associated with e.g. the Red Cross' Paypal account, you can craft Paypal URLs which cause people to go to Paypal, send money directly to the Red Cross, and then come back to a page under your control.  This is only minimally secure but, again, what are you worried about security for here anyhow.