Reaching your goal weight doesn't mean you're finished with your diet. It's very easy to gain all the weight back and happens quiet often to many people (95% is often quoted). That is why the Excel Diet never ends. If you find a weight-loss program that doesn't continue after you've lost the weight, then you've found a weight loss program that won't work.
On the Excel Diet say your goal is 160 and the most you've gained in one day is 3 pounds. Set your goal for 157. Continue to weigh yourself each day. Make sure you continue to moderate your food intake and activity to keep a stable weight instead of trying to lose a pound a week.
Start a brand new spreadsheet and put your goal as your current weight, say 157 in this example. Change the pounds to lose to zero.