How to exclude prequery results

Hi,

I would like to define a query, to see which customers did not generate revenue within a certain period.

Now, I have defined two queries: One, to see which customers DID generate revenue, and another, which should display all customers, EXCEPT the ones that were selected by the first query.

The results from the first query are passed to the second by a variable, but, I cannot switch the sign to "exclude from selection". Why is this option greyed-out and how can circumvene this?

Does anybody know the answer?

Kind regards,

Sascha Zevenhuizen