This looks useful for anyone working with cubes in MS Excel. It allows advanced users to create their own custom private calculations, and view the MDX being executed within a pivot table.
OLAP PivotTable Extensions is an Excel 2007 add-in which extends the functionality of PivotTables on Analysis Services cubes. The Excel 2007 API has certain PivotTable functionality which is not exposed in the UI. OLAP PivotTable Extensions provides an interface for some of this functionality. It can be launched from the following menu option in the right-click menu for PivotTables: