Thanks! I know how to do this. But how can I do this when the field is just calculated (not part of another table)? Should i created a new field in the original table? How?
There are two options I can think of:
Use nested queries, and in a new query refer to that table and the calculated field from this query, and join them there.
Or (probably better, depending on your field):
Refer to the table only, but where you import the primary key (or whatever field you want to match), have the criteria as:
=(whatever your sum is)