How to change Quantity on a orderline in Dynamicweb ECom

You should create an URL which contains:

URL: The page which contains the shoppingcard
CartCmd: 'orderline' - tells Dynamicweb that you want to alter an orderline
quantity: The quantity you wish to add(!), so to go from 10 to 2 set it to -8 (!)
key: The orderlineID - get from DW templatetag:

Example:
http://www.myshop.dk/default.aspx?id=4131&CartCmd=orderline&quantity=10&key=OL2148