SUM function based on User-specific filter

Ok, here's the situation:

- I have a transaction module

- The transactions are children of Cost Centers

- The transactions feed into a reporting module using a SUM function

- There are certain "special" cost centers that exist across different functions\parents in the Cost Center list

- I need to be able to give the users the option to: 1 - Only show the values for those "special" cost centers 2 - Show values excluding those "special" cost centers.

I thought I had this solved.  I created a attribute that identified that "special" Cost Centers, a module to allow users to choose how to filter those "special" Cost Centers (filter and exclude) and incorporated those selections in the SUM formula.  It worked great until I realized that the filter selection applied to ALL users.  I need it to be user-specific.  

Given my situation, is using a filter and incorporating that into a SUM formula that right path?  I've considered an alternate hierarchy, but looks like a bunch of maintenance and tricky to maintain with the transaction detail and I think that would require separate dashboards.  If the filter and SUM are correct, how do I do that?  I have set up a user-specific filter, but I don't see how I can apply that filter to my SUM formula.

THANKS