thanks for the reply Jason.
I got it working, (with a cookie for now), I am passing the selected id's back as a filter into a lookup recordset and the items are added to the cart in a loop.
Only thing is, with the ecart get from recordset server behavior, there is no option (i can see) if an item is already in the cart.
I tried adding _AddIfIn=0 manually, but this doesn't work, whatever I do, i can only add one of each item to the cart