This may be simple for everyone else except for me.

I have a spreadsheet in which each column I can fill in one of three options
(N/A, Yes, No). This is done with a list drop down box.

I would like to make sure that if I put "N/A" in A1, then B1, C1, D1, etc
are also N/A.

I would like that if I put "Yes" or "No" in B1 when I already put "N/A" in
A1, B1 would be highlighted in some what that tells me I created an error.

Any solution which addresses what I would like to happen will be really
appreciated.

Thanks for your help in advance.