Matrix Showing Distinct Count in Subtotal Row ONLY

Hello,

I am trying to make a Matrix table that shows the count of students enrolled at a University over several semesters. For the actual values themselves, I want the Count (including duplicates). However, for the column subtotals, I want it to show Disctinct Count. Is there a way to do this? Basically, I want the "Total" value in the matrix table to be equal to the numbers displayed on the line graph for each year. 

You can see, for example, that if I used distinct count (which is what my line graph is filtered to), the Total should be ~15,000 for year 2011, but currently in my matrix is it ~25,000. Is there a way to change only subtotal to Count (Distinct)?