Use the Modify Item Promotion window to set up promotions (enter items, set the promotion price, assign a start and end date, and so on). You can also use this window to modify existing promotions. Changes can be made on an individual basis by clicking a field in the grid. Or you can select the option to make global changes from the Misc menu. Global changes allow you to enter a change once and have it applied to all items on the promotion.
You can set up Eagle Alerts for when promotions start and end. See options 3311 and 3313 in the topic "Setting Up Eagle Alerts Options."
