Excel IF with text as option for cell as well as numbers

I'm trying to write an IF statement for Excel which is based on:

IF E93>E88 put Yes
IF E93<E88 put No

E93 can also be have the text N/A in it based on some earlier calculations

If E93 has N/A in it then I want this new IF function to put N/A as well as the output into this new cell.

If have so far:

=IF(AND(E93>E88,"Yes"),IF(E93<E88,"No"),"N/A")

But I get a VALUE# error when E93 has the text N/A which is itself put there by another IF function. The function putting N/A into E93 is:

=IF((E81>=E84),E81-E84,"N/A")

Any suggestions would be most welcome