Inverting a filter

I really need to be able to turn a filter upside down, into a NOT of itself. Is this possible?

It's not a standard filter though, it's a User: Current filter, attached to a relationship.

I basically have a node type called Assignment, and it is referenced from another node type called Assignment_Ignored, which are created if someone clicks to ignore an assignment. I then have a View to show someone all relevant assignments.

The logic I have in my filters is:

Node: Published
NodeType: Assignment

AND

(AssIgn Relationship) User: Current

but as you can see, this will show ALL the published assignments when the current user DOES exist in the relationship list of AssIgn!!! I literally need to invert the last filter to say all published assignments so long as the user is NOT in the list of AssIgn..!

I appreciate my objects and logic might not be ideal, and I have warped the example a little to simplify it for this post.. but if anyone can shed ANY light on "not" or "exclude" filters (for the dynamic user reference filter) that would be amazing. Cheers.