Thanks for your response. For some reason, the subtotals do not calculate properly. I am trying to get percentages of a particular column value. That means the numerator and denominator are in the same column of data. The "Show values as" functionality calculates the percentages for each row total even when I select "% Of" and specify the field. The dialog box wants me to specify a base, which I don't understand.

So, for example, here is what columns look like:
Jan Feb
Signed up 10 12
Attended 8 9
Cancelled 1 1
Missed 1 2

What I want to see are the following ratios:

% attended 80% 75%
% cancelled 10% 8%
% missed 10% 17%

For some reason, the formula returns the percentage of the row:

% attended 47% 53%
% cancelled 50% 50%
% missed 33% 67%