an outer join would be perfect fort this but I do not beleive that Excel tables allow you to use that join type.
given the join limitation the only thing that comes to mind is to union the 2 togther and include a field that identifies the source for the row
group on the code field
create a formula for countng the ones from excel (using the new source code column mentioned above)
if sourcecode='excel' then 1 else 0
sum that at the group level and then excude anythiung that is >0 using the group selection criteria