[TYPO3-shop] articles / products - price recalculation

[Ralph Witte]

Hi all,
finally my shop displays different articles for one product. So far so good.
But if I choose an article in the product list the price is not 
recalculated based on the price of the article.

The situation:
1. One product with image,info etc. and three sizes (entered like: 
100ml;250ml;1l;12,5l into product field: variant 2)

2. 3 articles with there own itemnumber and price (title = variant)

3. In list view, single view and basket all different sizes are available.

4. I want to have the price changed according to the size I choose.

Can anybody help me out?
Regards
Ralph