ok, in this case, leave the discountable column value as 1 for both products and use the triggers:
Presence of item in cart:
if Item '<ID for prod 1>' 'exists' in the cart
AND
Presence of item in cart:
if Item '<ID for prod 2>' 'exists' in the cart
where <ID for prod 1> and <ID for prod 2> are the ID values for the 2 products. leave the calculation as described before.