A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data
A formula can only return a result in the cell that contains the formula, not in another cell.
If you want to be able to enter data in F6 but have it change to "NA" if D6 contains "Y", that would require VBA code.
This would work in the desktop version of Excel for Windows and Mac, not in other versions, and it would require users to allow macros.
Would that be OK?