Care to share what type of spreadsheet you were working on? Personal or business?

A few years ago, I found out by accident that they have a Microsoft Excel World Championship, aka "Excel Olympics." It's far beyond my skill level but quite an interesting concept.

I do similar things to you when trying to focus. Turn off phones, turn off email, close my internet browser. A big one is notifying co-workers that I'll be focusing on an important project and request not to be disturbed.