Queries :: Adding Amount For Each ID Per Month

I've got a table with a lot of data.

In the table is a SAP Number (ID), a booking date (BuchDatum) and an amount (Betrag)

Now i want to sum up, for each ID the amount in one months.

In the end i want to have a table like this

Date SAP Number Amount
01/2011 12345 1000€
02/2011 12345 0€
03/2011 12345 100€
04/2011 12345 300€

and so on.

So for each ID, a table like this.

I tried it already, but my Problem is that i either sum up the years or the months. I Need a combination.

I put the file in the Appendix.