Get first non-null values for all customers

Hi,

I am using SQL 2008R2, the Adventure Works database and I need to retrieve the first date with non-null Sales Amounts for each customer. The query is the following:

SELECT
{
     [Measures].[Sales Amount]
} ON 0,
NONEMPTY
(
     [Due Date].[Date Key].&[20010701]
    :[Due Date].[Date Key].[All].LastChild
    ,{
         [Measures].[Sales Amount]
    }
).ITEM(0)
ON 1
FROM [Adventure Works]
WHERE
(
    [Customer].[Full Name].&[11000]
)

While this correctly returns the first date in the specified interval with non-null sales amounts for customer 11000, I would need to achieve this for all customers and this is where I get stuck. So I need to incorporate the Customer dimension in the SELECT statement somehow and remove it from the WHERE clause.

Any help would be greatly appreciated!

Thank you!