You’ll find it under the Formulas tab, in the Formula Auditing group. Once you open it, just hit Add Watch and select the cells you want to monitor. The pop-up will show you the sheet name, cell ...

I remember reading a story about how Tom Sawyer painted a fence. He was a naughty and intelligent boy, created by Mark Twain, when he wrote The Adventures of Tom Sawyer in the 1870’s.