Google Spreadsheets Get Data Validation

Google has added data validation (lenient or strict) to Google Spreadsheets. You can now:

• Validate numbers, dates, and text.
• Prevent users from entering text that doesn't match your criteria, or show them a comment on the cell when the data doesn't match the validation rule.
• Add text to the cells you add validation to, to help your collaborators enter the right type of data.

Learn more here.