Partial Sum

I wan't access to calculate partial sums based on dates(formatted american style here), in particular, the amount ordered of a certain product until a certain date instead of the amount ordered at a certain date. So:

product date amount
a 01-01-2005 1
b 02-01-2005 1
a 07-01-2005 2
a 10-01-2005 1
b 01-02-2005 4
b 01-03-2005 1

Should become:

product date amount
a 01-01-2005 1
b 02-01-2005 1
a 07-01-2005 3(=1+2)
a 10-01-2005 4(=1+2+1)
b 01-02-2005 5(=1+4)
b 01-03-2005 6(=1+4+1)

I have done it with the following query:

SELECT tespartialsum.produkt_nr, tespartialsum.transdate, tespartialsum.amount, Sum(tespartialsum_1.amount) AS SumOfamount
FROM tespartialsum AS tespartialsum_1 INNER JOIN tespartialsum ON tespartialsum_1.produkt_nr = tespartialsum.produkt_nr
WHERE (((tespartialsum_1.transdate)<=[tespartialsum].[transdate]))
GROUP BY tespartialsum.produkt_nr, tespartialsum.transdate, tespartialsum.amount;

it works, but only on a restricted version of the table. I want to do it faster to be able to do it for the entire table(70000 products, 1000.000 lines).

Please help..