On the ribbon tab Review | group Input validation, you will find commands that can be used to detect cells that contain a invalid data.
Note: A cell contains invalid data if the command Input validation 
has been used to specify which values should be allowed in the cell, and the current cell content violates any of these rules.
To find and analyze such errors, use the following commands in the command group:
▪ Input validation
| Opens the dialog box Input validation for defining allowed values. See previous sections. |
▪
Mark invalid data
| This command paints a red circle around each cell (on the current worksheet) that contains an invalid value. |
▪
Remove (invalid data) marks
| Removes all red circles (from the current worksheet) added with the above command. |
▪
Previous invalid cell
| Jumps to the previous cell that contains an invalid value. |
▪
Next invalid cell
| Jumps to the next cell that contains an invalid value. |
Notes
▪The marks for invalid data also appear in the printout.
▪However, the marks are not stored in the document. Thus, when you save a document, close it and open it again, all circles are removed.