this should work

with member [Measures].[x] as

case [Measures].[measuregroup]

when [Date].[Date Id].&[20110101] then '[Measures].[x]'

else '0'

end

Select [Company].[Company] on 0,

[Date].[Date Id] on 1

from [cube]

where [Measures].[x]

try defaulting to different number other then null