I want to divide a number by counta for certain cells (which would yield a
number). For example, =10/counta(A1:A4) would equal 10/4 if cells A1 to A4
are filled.


What I am stuck on is this:

=10/counta(A1:A4 but exclude the cells from this range that equal any of
the numbers in in the range B5:B8)

Example:
=10/counta(A1:A4) would be 10/4
but since A2 = B7, the formula gives me 10/3 because A2 is excluded from
counta