I found a solution: In the code for
// WA eCart AddToCart
I changed
...
$ATC_itemPrice = floatval("".$row_rsArtikel['Preis'] ."");// column binding
...
to:
...
if ($row_rsArtikel['Aktion'] == 1) {
$ATC_itemPrice = floatval("".$row_rsArtikel['PreisAktion'] ."");// column binding
} else {
$ATC_itemPrice = floatval("".$row_rsArtikel['Preis'] ."");// column binding
} ;
...
That was quite easy :-)