Alertpay autopayment system

Hello I need an automatic system of payments, when a user takes into account $ 20 (for example) by clicking on a link that will send that amount of money to his account alertpay. As you will understand it has to be a very safe system, an encryption system would also be interesting, I'll give the necessary files from the Web so that it is well integrated. One last thing, in the administration section of an option to return to the payments by hand if any problems occurred.