Canceling a Query

I'm working on an application for work where users will be querying the database to get information back about processed documents. I'm trying to set up a way for a user to cancel a query which is taking too long. I'm using MS SQL Server 2000. The interface for the cancel is easy enough, a form containing a button that says 'cancel' and a value or set of values identifying the query being run. I've found 'KILL <SPID>', but the problem is that all the connections to the database are done through the web-server so they get the same SPID, which means that EVERY query being run by EVERY user gets killed. (Obviously not an acceptable solution.) Does anybody out there know of a way to specifically kill a single query/stored procedure? We're willing to track as many values as necessary to do it. Thanks. - Theo