I have put an rank function in place which works as follows (column A in my
worksheet)

=RANK(AC3,AC$3:AC$134,0)

This works fine, except I want it to come up with a value of N?A if the
number in Column AC equals 0. So I tried the following (Column A on my
worksheet)

=IF(AC3="0","N/A",(RANK(AC3,AC$3:AC$134,0)))

This made absolutely no difference, all the 0 values still appear with a
number appearing instead of N/A.

Is there something glaringly obvious I am doing wrong?