What you mean is that the test is a "negative test" and YOUR test PASSes when the negative test performs as you expect, and fails.
The problem is to keep the sense of PASS and FAIL separate. If you want to record that a test PASSes when it makes an error, then the way to trap that is to lay an OnErrorGoScript command in the test script file AHEAD of where you antitipate an ERROR state.
Now, when the ERROR occurs, control goes to a script page of your choosing. This one should be set up to end normally. The normal (non-ERROR) termination of the test will be seen as a PASS by the eV.Manager module.