Instead of using defecation as a way of determining when to feed, you should just set a schedule based on time. Snakes can be very irregular in their "pooing". Typically (and everyone has a different view on feeding) corns are fed 4-5 days when on pinks, 6 days on fuzzies, 7 on hoppers, and 7-10 days on anything larger. Do keep in mind that both people and snakes vary so you may hear different things.
Welcome to the forum though and try the "search" function, it can be a life saver!!