Sum and Pivot Tables

[#1]

I was hoping someone could point me in the right direction. I have a pivot table and I'm trying to get the sum of estimated revenue for different events for various business units. Since events can span multiple months, I only want to show the estimated revenue for the month/year selected by the user. For example, if a show for a given business goes from 4/30/2010 - 5/2/2010 and has an estimated revenue of 30k, when a user has selected May of 2010 in the selection criteria, the estimated revenue for the selected month should display 20k (10k average per day * 2 days in May). Here is the formula that I am using to get these values:

(((EstimatedRevenue) / ((EventEndDate - EventStartDate) + 1)) * COUNT(UtilizationDays))

The formula works correctly but there aren't any subtotals or grand totals in this column of the pivot table. I believe the problem is that there are multiple business units and each can have multiple shows. I tried using the sum functions in different parts of the formula, but it either doesn't show the subtotals/grand totals or the values of the estimated revenue displays '-'. Does anyone know what I need to do to make this pivot table work?

Thanks!