I first learned this tip about a decade ago and had long forgotten it until reminded today.
When working in Microsoft Office Excel (any version), you can instantly change the view so that formulae appear in each cell instead of the results they generate. To do this hit CTRL+` (that’s the accent key, normally the upper-leftmost key on your keyboard). Hey presto, your formulae are served! To revert to the normal view again, just press CTRL+` once more.
The Formula Auditing toolbar that appears is another handy side effect to this keyboard shortcut. Have a play to discover how easy it is to trace any errors in your formulae.