This topic has been brought up a few times. There seems to be a few issues that would make this a tricky task.

ybiC requested this feature a while back and it was implemented(?) soon after.

I don't see the option in super search however. Maybe this feature was once a part of the search but was later removed when super search was refined. I'm not sure.

Upon closer inspection, however,there is a checkbox in your user settings that allow you to filter your search results.

What exactly this feature means, I'm not sure. But it sounds like it might be something worth investigating.

Update: I knew I had seen this discussed fairly recently. Take a look at this thread and kudra's reply which shows you a work around for this.

- wil