Excel: Building Resilient Spreadsheets
Like Duolingo, but for Excel: Building Resilient Spreadsheets. Tomo turns the whole topic into a game you play five minutes a day, until it actually sticks.
For the part of you with thirty open tabs that never became anything.
A short one: 11 levels across 2 sections, about 22 minutes end to end, roughly 4 days at five minutes a day. It moves through Making Formulas Resilient to Breakage and Designing Sheets That Don't Collapse Under Change. It assumes you already know the basics.
Free forever · No credit card · iPhone & Android
Key ideas in Excel: Building Resilient Spreadsheets
- VLOOKUP uses fixed static integers that do not shift when new columns are inserted.
- XLOOKUP points directly to explicit range references that Excel dynamically tracks and shifts.
- Hardcoded index references return neighboring column data instead of throwing a visible formula error.
- Approximate match assumes data is sorted ascending and stops scanning at the first higher value.
- Unsorted lists cause binary search logic to jump unpredictably and return the wrong row's value.
- Excel does not validate whether a table is sorted before running an approximate lookup.
- IFERROR conceals critical syntax issues like mistyped formula names (#NAME?) and deleted cells (#REF!).
- Targeted functions like IFNA trap only lookup misses without hiding formula bugs.
- Overusing IFERROR makes debugging broken models difficult because valid syntax failures masquerade as blank cells.
- Two-way INDEX MATCH uses two separate MATCH functions to find row and column numbers dynamically.
- The outer INDEX takes the two MATCH outputs as its row_num and column_num intersection coordinates.
- Dynamic headers eliminate hardcoded matrix cell coordinates like C4 or G12.
- Excel ignores text cells entirely during SUM functions rather than returning an error code
- COUNTA tallies non-empty cells regardless of whether Excel stores content as text or numeric
- Converting text digits to actual numbers requires operations like VALUE or multiplying by 1
- Excel's standard TRIM function removes standard space characters (CHAR 32) but misses CHAR 160
You've tried the other tabs
Thirty open tabs. Four facts you actually kept.
You watched. You nodded. By Sunday it was gone.
One answer, then back to scrolling.
Eight weeks. You meant to finish. You didn't.
Tomo gives Excel: Building Resilient Spreadsheets the Duolingo treatment: levels, streaks, and quick quizzes that test what you just learned. That game loop is what the tabs above never had, so it's the one you actually finish.
Here's what playing it feels like
A real question from this course. Take your best guess.
Why does an XLOOKUP keep returning the right column even after someone adds columns to your table?
Get it right to open this lesson and 10 more in the app.
Where Excel: Building Resilient Spreadsheets takes you
Stop wrestling with broken lookups, silent calculation errors, and fragile layouts. Learn practical spreadsheet habits to make your workbooks reliable, auditable, and easy to maintain.
- 1
Making Formulas Resilient to Breakage
- Replacing Fragile Lookups and Broad Error Masks
- Spotting and Neutralizing Silent Data Traps
- 2
Designing Sheets That Don't Collapse Under Change
- Structuring Tables and Data Boundaries
- Multi-Condition Summaries and Dynamic Arrays
2 sections · 4 units · 11 levels. Built to play, not to enroll.
You pick the voice
Excel: Building Resilient Spreadsheets is taught in the The Bestie style: your friend who just gets it. Want a different feel? In the app you can spin up the same topic in any of Tomo's teaching styles. Same facts, totally different vibe.
More Business on Tomo
Solopreneurship: Building the One-Person Engine
Master the mechanics of starting and running a business entirely on your own. Learn to design value loops, manage unit economics, and build automated systems that scale without a team.
Building a Resilient Portfolio
Move beyond basic index funds to understand the mechanics of risk, tax efficiency, and market cycles. Learn to evaluate individual assets and manage your wealth with professional-grade discipline.
Trading with the CCI
Learn to use the Commodity Channel Index to spot market trends, identify overbought conditions, and find high-probability trade entries.
Mastering Your Money
Stop guessing and start building wealth with a practical approach to the market. Learn how to avoid expensive mistakes and use the math of growth to your advantage.
Investing: Your First Portfolio
Stop working for your money and make your money work for you. Learn how to build a simple, automated portfolio that grows over time without the stress of picking stocks.
Building a Community Hub: Coffee, Flowers, and Faith
Learn how to launch a mission-driven coffee shop and grow it into a multi-purpose space for groceries, flowers, and worship.
Start Excel: Building Resilient Spreadsheets today.
Download Tomo, search Excel: Building Resilient Spreadsheets, and play your first lesson in under a minute.