Counting number of aoccurance in a table

[Yee]

Dear Anyone

I have two list, ListA(horizontal list)and List B (vertial
list) Both hold text values

List A is a master list, each cell holds a distinct
value.,ie. A,B,C,D...

List B is a user list, each cell may hold duplicate value.,
A,A,B,B,B,B,C,SL

How could write a function to count the number of
occurance of the values in List B that are defined in List
A.

Hope you understand what i mean.

Many thanks in advance

 

[Peo Sjoblom]

=COUNTIF($A:$A,B1)

Copy across