Use Validation to Keep a Beginner Workbook Consistent

Describe what a cell should accept

Data validation can restrict worksheet input to suitable types or values. The source lists possibilities including numbers within a range, dates, text length, and predefined lists. These controls are useful when a workbook will be completed by several people or maintained over time. Establishing the acceptable input at the beginning can reduce the cleanup required after inconsistent entries have spread through the table.

Keep the rule aligned with the workflow

A validation rule should support the actual information being collected, rather than impose an arbitrary restriction. Decide which cells require the rule, how the accepted values are defined, and how someone will know what to enter. The article also covers copying, reviewing, fixing, and removing validation. Treat it as part of the workbook's design and maintenance, because a rule that no longer fits the task can become an obstacle instead of a safeguard.