If i have a value in a column can i then in the next cell while keeping my list range allow only specific columns to change?

I have a column in excel that gives three options. "Y","N", or "NA".

If I select "N", and not "Y" or "NA" I want the next cell to allow me to pick from another list "N", "Y", "NA".

However if I don't pick "N" i want the cell to automatically say "N/A" from the three options. Then give me an error message if i click "Y" or "N" from the list.