Excel LET & LAMBDA: Readable Formulas, Custom Functions & MAP/REDUCE

What you'll build

What you will be able to do

Each lab ends with a concrete result that you build yourself and the checker confirms, cell by cell.

• Calculate net value, shipping and order totals for Alder & Finch with LET, so each formula names its steps and calculates the net value only once.
• Write small LAMBDA functions for Alder & Finch's catalogue (inches to centimetres, footprint, volume, shipping class) and call them directly in the cell, also from a LET variable.
• Use Alder & Finch's custom functions TaxPrice, MarginPct and Discounted like built-in functions, nest them, and test a new Markup function inline before it gets a name.
• Summarise Alder & Finch's H2 store sales with BYROW (total and range per store) and BYCOL (total per month and stores that hit the target), each as one spilling formula.
• Use MAP to set shelf prices, flag reorders with category-specific limits and pick homepage items with AND, then total the featured stock value with SUM(MAP()).
• Build Alder & Finch's year-to-date sales with SCAN, grow a cash reserve with monthly interest, get the year-end balance with REDUCE and chart the running total.
• Generate three grids for Alder & Finch from a row and column number alone: a crate × pack-size table, a weekly showroom rota and an instalment plan.
• Rewrite Alder & Finch's unreadable commission formula with LET, test a flat IFS version as an inline LAMBDA, and total the plan with MAP and the named function Commission, always with identical results.