[Event Registry] Is there a way to check a correlation parameter for not being null?

I have an event task block, it sends a message and then starts listening for a message. I want to define its correlation parameters so that the task is only triggered when specified variables are received(i.e., are not null).

Is there a way to do that ?

The correlation only works on specific values, because it calculates a unique key based on the value to be able to do a performant lookup. So a any match, but not null is not supported.