Question of Excel formula if nested error

Question

I would like to make a formula on excel file which require to meet the following requirements:

1. If N column is empty, then nothing to do
2. If N column are not C and O, then show message of "invalid value" (Remark: A,B,D,E.....M,N,P,Q....Z)
3. If N column is C and T column is empty, then show message of "please write something here"

After run, it prompt up the error message of "You've entered too many arguments for this function". May I know what's wrong with me?

Thanks.

=IF(ISBLANK(N815),"", IF(OR(N815="C",N815="O"),"","Invalid Value!", IF(AND(N815="C",ISBLANK(T815)),"Please write something here!")))

Answer 1

Did you know that you can indent your formula in the formula bar? :)

=IF(
    Something is True, 
    then do something, 
    otherwise do something else
   )

It is much easier to write when you want multiple IFS

=IF(
   ISBLANK(N815),
   "",
   IF(
     OR(N815="C",N815="O"),
     IF(
       AND(N815="C", ISBLANK(T815)),
       "Please write something here!",
       ""
       ),
     "invalid value"
     )
    )