When it comes to handling validation for proper latitude in Excel, there are a few things you need to keep in mind. First and foremost, you need to make sure that the data you're working with is in the proper format. This means that it should be a number between -90 and 90, with no letters or other characters. If you have data that isn't in this format, you'll need to convert it before proceeding.
Once your data is in the proper format, you can begin validating it. There are a few different ways to do this, but the most common is to use the data validation feature in Excel. To use this feature, select the cells you want to validate, then go to the Data tab and click the Data Validation button. In the dialog box that appears, select the option for "Decimal" under Validate Against, then set the Minimum and Maximum values to -90 and 90 respectively.
Once you've done this, click the OK button and your data will be validated. If any of the values are outside of the specified range, you'll see an error message appear. At this point, you can either fix the invalid data or delete it as needed.
If you want to take things a step further, you can also add a custom error message that will appear when invalid data is entered. To do this, simply select the cell(s) you want to validate, then go to the Data tab and click the Data Validation button. In the dialog box that appears, select the option for "Decimal" under Validate Against, then set the Minimum and Maximum values to -90 and 90 respectively. Next, click on the Error Alert tab and check the box next to Show Error Alert After Invalid Data Is Entered.
In the Title field, enter a brief description of what's wrong with the data (e.g., "Invalid Latitude"). Then in the Error Message field, enter a more detailed explanation of what needs to be done to fix it (e.g., "Latitude must be a number between -90 and 90"). Finally, click on the OK button and your custom error message will appear whenever someone tries to enter invalid data.