The Filtervalues function is extremely useful but has a frustrating limitation.
Currently it only allow you to return all values in List A that exist in List B.
We need at least, the opposite: All values in Lisit A that are NOT in List B.
A list of CustomerID values for a region.
A list of CustomerID value who meet some criteria.
For example: were recently sent promotional material.
Which customers in List A have NOT received this mailing?
A few people (including me) have addressed this with custom functions but the functions are inefficient as compared to a native feature.