A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
To make sure something is selected in Data Validation make sure Ignore Blank (Data Validation > Settings) is NOT checked.
To make blank cells red:
- Select all cells that must not be blank.
- Use Home (tab) > Conditional Formatting (icon) > New Rule
- Select Format only cells that contain
- In Format only Cells with: select Blanks
- Set format to red fill.