Parameterized SSRS reports sourced from OLAP cube with a dimension having set a default member

Imagine you develop SSRS 2008 reports based on SSAS olap cubes and face the following situation: a default member on a dimension, let's say the Date dimension.The report uses a parameter and it's default member is based on it ( typically the last date where the system has a non empty measure).User picks up the default member for the date dim. and another date - in order to see the aggregated results - but only the results for the default member are displayed