Data Validation in a Custom setting and forcing Upper Case

Hi All

Just wondering if i want to apply data validation to a cell in a spreadsheet
but I want to use a drop down list.

I have added a custom validation, used the Upper function and can reference
only 1 cell from the sheet, if I want to reference multiple cells I have to
use the exact function as this can then cope with the OR operator for the
other cell entries in the list whereas the upper function won't allow the use
of OR and therefore I can only reference the one cell.

All ideas would be welcome.

Thanks
Ailish