Hi Tom,

If the Data Validation option is greyed out, it could be due to a few reasons. Here are some possible solutions:

1. Check if you have selected a cell or range of cells that already have data validation applied to them. If so, you won't be able to access the Data Validation option until you remove the existing validation. To do this, select the cell(s) and go to Data Data Validation Settings, and then click on the Clear All button.
   
2. Check if the worksheet is protected. If the worksheet is protected, you won't be able to access the Data Validation option until you unprotect the worksheet. To unprotect the worksheet, go to Review Unprotect Sheet, and then enter the password if prompted.
   
3. Check if the workbook is protected. If the workbook is protected, you won't be able to access the Data Validation option until you unprotect the workbook. To unprotect the workbook, go to Review Unprotect Workbook, and then enter the password if prompted.
   
4. Check if the file format is correct. If the file format is not correct, you may not be able to access certain features, including Data Validation. To check the file format, go to File Save As, and then select the correct file format from the dropdown list.

I hope one of these solutions works for you. Let me know if you have any other questions!