Beginner level · Module 1: Reliable Formulas and Excel Tables · Lesson 3 of 3
Validation and Error Handling
Stop bad data at entry with data validation, and handle formula errors cleanly.
In this lesson you will
- Set data validation rules and drop-down lists
- Interpret Excel errors and use IFERROR appropriately
Key concepts
data validationdrop-down list#N/A, #DIV/0!, #VALUE!IFERROR
The lesson
Data validation restricts what can be typed: whole numbers above zero for quantities, dates within the month, or a drop-down list of branch names from a table. Add an input message and a clear error alert.
Learn what errors mean: #DIV/0! is division by zero, #N/A means a lookup found nothing, #VALUE! means the wrong type of value, #REF! means a deleted reference.
IFERROR(formula, alternative) replaces errors with something useful, but use it carefully: hiding every error can also hide real mistakes. Handle the specific case you expect.
Step by step
- Add a drop-down list of branches from a table.
- Restrict quantities to whole numbers above zero.
- Trigger and identify four error types.
- Use IFERROR where an error is expected.
Practice activity
Complete the validated sales sheet from the practical activity with a clean summary block.
Expected result: Invalid entries are blocked with clear messages, and the summary shows no unexplained errors.
Check your understanding
-
What does #N/A usually mean in a lookup?
Show answer
The lookup value was not found.
-
Why use IFERROR carefully?
Show answer
Hiding all errors can hide real mistakes.
Taught live by an instructor — online or in person. Free course lessons are for self-study and do not lead to a certificate — see registration options.