The short answer is yes, with custom MDX, but it wont be simple or easy to maintain. A much superior solution is to create dynamic sets using MS ProClarity Desktop Professional. ProClarity is now part of the MOSS 2007 Enterprise Edition CAL. Don't be afraid to use it.
PDP will allow a user to create a dynamic set using the ProClarity Selector, a simple wizard designed for business users. Members of that set are dynamically generated at runtime. The script for the dynamic set set can be edited by a business user, adding and deleting steps, rearranging execution order.
Dynamic sets can be published to the ProClarity Server (also part of MOSS now) as shared items and used to create analytic views (in PAS) that can be served up and filtered right inside a PerformancePoint 2007 dashboard (also now MOSS 2007). As a shared item one set definition can be used in multiple analytic reports with one point of maintenance and security.
I will add some screenshots and examples of dynamic selector sets to another post next week.
With the inclusion of PerformancePoint and Proclarity into MOSS there is an incredible amount of BI capabilities free inside the box. You just have to consider and evaluate which tools best fit each of your separate BI needs to create a composite solution.
I hope this helps.
Pete