How To Overlay Different Totals Figures With Filters

I am doing a budget sheet in Excel for the different expenses accrued by the different classes we offer in our university department (honoraria for guest lectures, tickets to shows or museums, etc.). The sheet is formatted as a table and I have the Total Row enabled at the bottom.

However, we have a reserved budget for different things. For instance, Fall 2013 museum tickets has, say, a budget of $1,000. Fall 2013 honoraria might have a budget of $2,000. I want to be able to filter to see only Fall 2013 honoraria: the totals row will reflect this, but I also want it to automatically tell me how much money is left in that budget (i.e. I want it to know to subtract $2,000 from the totals figure because that is the budget for Fall 2013 honoraria).

It gets a little more complicated because we also have a budget for each class too. One class might have both honoraria for guest lectures and field trips to a museum, and we might say "We don't want this class to spend more than $500." Again, I want to filter to see just this class, and have the Totals row also show me how much money is remaining for this class.