I have an event whether an item sold will be returned or not which I can predict with a certain probability based on information gathered at the time that the purchase occurs (product features, customer information, time and place, etc). So: P(Return | transaction information) = x% for a specific unit soldI also have a historical time series of total units sold for that item, and a future forecast of sales of that item over the next few weeks. Assuming I gave the relevant transaction data for each historical sale that occurred, is there away to generate a future forecast from the return probability, so that I can state with some confidence that I will get 15% total returns on the item next week, 10% the week after etc? 
How can one generate future forecasts from probabilistic events?
time series;forecast