mdx: display all when empty

i just want to display the all tuple string - to be used in filtering, when filtered metric is null.
this has to be possible...

adventure works example:

with

MEMBER [Measures].[ParameterCaption] AS [Product].[Product Categories].CURRENTMEMBER.MEMBER_CAPTION
MEMBER [Measures].[ParameterValue] AS [Product].[Product Categories].CURRENTMEMBER.UNIQUENAME

select
({
[Measures].[Order Count]
,[Measures].[ParameterCaption],[Measures].[ParameterValue]
})
on 0,
({
[Product].[Product Categories].[All]
})
on 1

from [adventure works]

where
(
[Ship Date].[Calendar Year].&[2004]
--,[Ship Date].[Calendar Quarter of Year].&[CY Q1]
,[Ship Date].[Calendar Quarter of Year].&[CY Q4]
)

run the above code - displays null for everything
Order Count ParameterCaption ParameterValue
All (null) (null) (null)

uncomment q1, comment q4 - displays values for everything

Order Count ParameterCaption ParameterValue
All 6,128 All [Product].[Product Categories].[All]

for q4 when no results exist, i want this to be displayed:

Order Count ParameterCaption ParameterValue
All (null) All [Product].[Product Categories].[All]


Any suggestions?
Obviously, I am not an mdx expert... ;)

Thanks, Megan