count and divide query

Hi,
I have a query looking like this:
      SELECT        dbo.shopCart.product, COUNT(dbo.shopCart.productID) AS Antal
      FROM            dbo.[Order] INNER JOIN
                                           dbo.shopCart ON dbo.[Order].orderID = dbo.shopCart.orderID INNER JOIN
                                           dbo.[Order] AS o ON dbo.[Order].orderID = o.orderID
      WHERE        (dbo.[Order].customerID IS NOT NULL)
      GROUP BY dbo.shopCart.product, dbo.shopCart.productID
      ORDER BY antal DESC
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That conts how many products that has been sold per productID. I would like to add a field that counts the percentage rate of the row productIID as compared to the whole sale (all productIDs).

I would like my result to look like this:
Product               Antal           %
A product           1000           10%             (the total sale is 10 0000 products)

Is there a way to achieve this?

Thanks for help!

Peter