I am not used to working with Excel. This is what I want to happen, but I am
not sure how to translate it into Excel.

I Have a colum with order sizes of our companies product. So colum A is
values between 1 and 2000 units. I want to see this:

Total Units sold = X
% of X that were orders of 1-150 units
% of X that were orders of 150-300 units
% of X that were orders of 300-600 unites
% of X that were orders of 600-1000
% of X that were orders of 1000+

I can input them manually by typing "=SUM(A1:A12)/X" but each time I add an
order I have to redo them all.
So what I need is something like:

=SUM(ColumA) WHERE VALUE is equal to or less than 150

Can anyone help me with this?