=(SUM(I5:U5))+F5-(COUNTA(I5:U5)*15)

this gives me a plus/minus balance for a team roster in Col A, dates are in
the range, which is added if they paid money or counted as present if there
is an x in the cell, F5 is a credit cell, and the count is $15 per session.
Now if I get enough people, I only need to charge $10 each week. Any ideas
on how to maybe mark the column the amount charged and have the plus/minus
work?
somehting like a counta-ifs function?