UrlScan is installed as a global ISAPI filter. You can unregister it from the IIS Manager UI and then reregister it when you want to run it again. Alternately, you could uninstall it. The uninstaller will not delete your urlscan.ini file or your log files. If you then reinstall it, it will run as it did before.
Regarding an IP exception list, UrlScan does not have that feature. One of the reasons for this is that IP addresses can be spoofed. It would be possible for an attacker to get malicious requests past UrlScan by doing this.
Thanks,
-Wade
PS: UrlScan 3.0 released today. See the announcement at the top of this forum.