Custom Targeting: Allow for Boolean Logic in Symbols

This is potentially an edge case, but I just had a need for it arise, so I thought I'd submit it. What I'd like to see is the ability to exclude targeting parameters like URL Path.

Example: I have a Section (an Announcement Bar) that I'd like to show if utmSource=facebook, but NOT on certain pages. Unfortunately, it looks like URL Path can only be set to one of: [Is, Contains, Starts With, Ends With]. It'd be nice to have at least a Is Not, but it'd also be handy to have a Not Contains.