当源是SSAS多维数据集时，在Excel 2007数据透视表中使用“显示值为”选项？

I have an Excel 2007 pivot table showing "Year" across the top and "Month" down the side. What I am trying to do is represent the values as "% Difference" from the same month of the previous year. (Ex. If Jan-07 is 0,000 and Jan-08 is 0,000, I would like Jan-08 to show '20%'). However, every time I try to do this (using the "Show values as" tab of Value Field Settings) all of my numbers go to '#N/A'. Is there a way to do this using an Analysis Services cube as the data source? When I do this exact same thing using data on a different sheet as the data source for the pivot table, it works fine.I have an Excel 2007 pivot table showing "Year"