Is it possible to use the "does not contain" logic using vstest TestCaseFilter?

Question

I am using vstest TestCaseFilter to run custom unit tests in VS 2013.

My goal is to run all tests with categories that do not contain a specific string.

From what I have read so far ( here ), the supported operators are:

= (equals) != (not equals) ~ (contains or substring only for string values) & (and) | (or) ( ) (paranthesis for grouping) 

Filtering all categories containing a string is trivial, but how do I get the opposite?

Could not find a way to achieve this so far ...