Articles with the highest sales for each year --> Filter?

Articles with the highest sales for each year --> Filter?

I've got a table with the categories "date of sale", "articles" and "sales".
Now I'd like to see only the top sale article for each year.
There are twenty or so different articles and the years are 2000 - 2004.
So far I set the "date of sale" fx(year) on the x-axis and the "sales" fx(sum) on the y-axis.
Then I set the articles for the color-option (that option next to the axis).
Now I've got a bar diagram that shows all the articles for each year, so you can barely see anything there.
I played with diverse filters for about an hour or so, but i still can't get it done.
I would be glad for any help.

Best regards
Frey