If you are working in a big sheet and want to monitor values in a cell which is far or in other worksheets, you can make use of Watch Window.
1. Go to Formulas Tab and click on Watch Window in Formula Auditing section.
2. Now Watch Window will appear.
3. Click on Add Watch to add cells which you want to monitor.
4. Now whenever a value changes in cells which you have added in Watch Window, the changed value will appear.