Sqlserver watch for time change

Hi this one is a bit strange so bare with me.

I have a table in SQL Server 2005 with a field called lock which will lock users from making changes to their data, this lock can be activated at various points throughout the app I am designing, however I have another column which means cut off date, basically the data can be changed between two dates. The start date is when the admins decide to open it out to everyone. I was wondering instead of using jobs, or a service is there a way to make sql server check its time against the cut of date time and mark the flag locked automatically. Almost like a file system watcher for sql server, baring in mind that I will have quite a few records all with different cut off dates.

Thank you very much for all your help and it something I think can be useful if it can be done that is.