TopCount issue

Hi,

I want to have the reseller sales amount for the most selled product on years 2001 to 2004,
I am getting null result with bellow query

with member [Top sales product] as
{
topcount(
[Product].[Product].[Product].members,
1,
[Measures].[Reseller Sales Amount]
)
} .Item(0)


select
{
Measures.[Top sales product]
} on columns,
{
[Date].[Calendar Year].&[2001],
[Date].[Calendar Year].&[2002],
[Date].[Calendar Year].&[2003],
[Date].[Calendar Year].&[2004]
} on rows

from
[Step-by-Step]