NoScript's base functionality works domain-by-domain, but the Application Boundaries Enforcer (ABE) can work on specific URLs and it's flexible enough to do what you want.
Here's the USER rule I used to get decent searching without breaking the rest:
Just add it at the end in
NoScript Options > Advanced > ABE > User.
Site line matches both the page you load and the URL used under the hood for Google Instant updates, so whether the combination of
INC() matches on the URL of the top-level request or the request being judged (NoScript's ABE docs aren't clear on this), it'll cause requests for new results without pressing Enter to fail.
SCRIPT in the
Site line may be the only ones you need, but I thought I'd play it safe.
If you want more details, the aforementioned docs are at http://noscript.net/abe/abe_rules.pdf