Automatic email sent to existing customers

Hi, I sell two products on Clickbank and I would like to set up some a automatic email system that uses my websites info email. Basically I need two setups to be made: Scenario 1 1. Customer buys Product A on Clickbank. After 1 week, he gets email number 1. This email contains a message about why he should consider buying Product B that I sell on Clickbank. If he buys Product B after reading this email, then he shouldn't get anymore future emails. If he doesn't buy Product A, I want to send him a second email 1 month later, again telling him why he should consider buying product B. Then 1 month later I send him the last email, a third one. Three different letters will be used. Scenario 2 is basically the same as above, except its reversed. After 1 week it emails the buyer of product B, telling him he should buy product A. If not bought, then it sends again after 1 month. And then 1 month after that if he still haven't bought Product A, I send him a third email. Three different letters will be used. I am open to hear what email solution works with this, I would prefer something that is free / very cheap. Please write a private message and tell me how you can solve this for me and why I should pick you. I prefer working with individuals. Thank you