KPI Filter - Set Default Value

I've got a dashboard setup in Sharepoint 2007 that uses a KPI List built from SQL Server 2005 Analysis Services. I've also got a filter tied to the KPI web part on my dashboard page.

The filter works fine when I select values and apply the settings, but I would like to set the default value on the filter to always be two items from the available list. When I select them as filter items, the filter text box shows "nre; nrm" as the filter text and the data is filtered correctly, but when I enter "nre; nrm" as the default value, the filter returns a "The default value specified is not valid" error message.

If I only use one value or the other (e.g. "nre" or "nrm" only) the default value works correctly, but I really need both values to be used as the filter criteria by default. How should I enter this in the default value field of the filter web part so that it will produce the results that I need