# Articles

## Formula challenge - multiple OR criteria

One problem that comes up a lot in Excel is counting or summing based on multiple OR conditions. For example, perhaps you need to analyze data and count orders in Seattle or Denver, for items that are Red, Blue, or Green? This can be surprisingly tricky, so naturally it makes a good challenge!

## Formula challenge - flag out of sequence codes

We have a simple list of 4-digit alphanumeric codes like A001, A002, A003, etc. What formula can we use to mark codes that are "out of sequence" with previous entries? This problem includes two separate challenges.

## Formula challenge - 2D lookup and sum

In this formula challenge, we have data showing cups of coffee sold at a small kiosk for a week. What formula will look up and sum the total cups sold after 12:00 PM on Tuesday and Thursday? Relevant cells are shaded in green.

## Formula challenge - build answer key for tests

In this formula challenge, we have four tests (Test A, Test B, Test C, and Test D), all with the same 19 questions, but listed in a different order. What formula can be used to match questions and construct an answer key for all tests? A perfect use for Excel's powerful lookup formulas.

## How to use INDEX and MATCH

INDEX and MATCH is the most popular tool in Excel for performing more advanced lookups. This is because INDEX and MATCH are incredibly flexible – you can do horizontal and vertical lookups, 2-way lookups, left lookups, case-sensitive lookups, and even lookups based on multiple criteria. If you want to improve your Excel skills, INDEX and MATCH should be on your list. See below for many examples.

## Excel custom number formats

Number formats are a key feature in Excel. Their key benefit is that they change how numeric values look without actually changing any data. Excel ships with a huge number of different number formats, and you can easily define your own. This guide explains how custom number formats work in detail.

## Formula challenge - difference from last entry

The challenge - calculate the difference from the current and last entry, even when previous entries are skipped. This is one of those problems that seems simple at first glance, but is tricky when you look closely.

## How to make dependent dropdown lists in Excel

One of the most useful features of data validation is the ability to create a dropdown list that let users select a value from a predefined list. But how can you make one dropdown dynamically respond to another? In other words, how can you make the values in a dropdown list depend on another value in the worksheet? Read on to see how to create dependent dropdown lists in Excel.

## Excel Data Validation Guide

Data validation can help control what a user can enter into a cell. You can use data validation to make sure a value is a number, a date, or to present a dropdown menu with predefined choices to a user. This guide provides an overview of the data validation feature, with many examples.

## Formula to list weekends only

Sure, you can use a complicated WEEKDAY formula to generate a list of weekends. But with WORKDAY.INTL, you can do the same thing with a WAY simpler formula. The trick is to use a special 7-digit "mask" to filter out all dates except weekends.

## Formula puzzle - sum payments by year

You have a fixed monthly payment, a start date, and a given number of months. You have five years shown on the worksheet. What formula can you use to sum total payments by year?

## Build friendly messages with concatenation

In this article, we explain how to use concatenation to display friendly and useful messages in your spreadsheets. The messages are dynamic and respond instantly to changes, so the effect is polished and professional.

## The EOMONTH function - Formula Friday

The EOMONTH function is one of those little gems in Excel that can save you a lot of trouble. It's a simple function that does just one thing: given a date, it returns the last day of a month. You can use EOMONTH to build all kinds of useful Excel formulas.

## Named Ranges in Excel

Named ranges make formulas easier to read, faster to develop, and more portable. They're also useful for data validation, hyperlinks, and dynamic ranges. This article shows you how you can use named ranges to build better spreadsheets, and better formulas.

## Replace ugly IFs with MAX or MIN

In this article, we show you how to replace a complicated IF statement with a clever and compact formula based on MIN or MAX. This is a great tip any time you need to choose the smaller or greater of two values inside a formula.

## Conditional formatting with formulas

Although Excel ships with many conditional formatting "presets", these are limited. A more powerful way to apply conditional formatting is with formulas, because formulas allow you to apply rules that use more sophisticated logic. This article shows 10 examples, including how to highlight rows, column differences, missing values, and how to build Gantt charts and search boxes with conditional formatting.

## 19 tips for nested IF formulas

Are nested IFs evil? Are they necessary? Are there alternatives? The answer is Yes! This in-depth article explores nested IF formulas in detail, with lots of tips, and several alternatives.