How do I make countif update in real time? For example, in column A1 I have
this formula:

=COUNTIF(A2:A5,"F")

in cells A2:A5 I have

F
P
f
X

My formula returns 2 IF the data is already present. But if I change the
data to:

F
f
F
P

my formula still returns 2 UNLESS I click on the cell the formula is in and
hit enter again. Then it will recalculate. But how do I make the formula
return the answer in real time like the SUM function does?