Getting rows where column has changed?

I'm trying to make a page to help in detecting people using automatic refresher programs. In the table that stores user info, there is a column called "lastseen" which says when the user was last seen. I'm trying to: 1. Select all lastseen colmns that are less than 5 minutes old 2. Wait 2 seconds 3. Select lastseen columns that have changed since step 1, and display that info Any ideas on how to do this? Is it even possible? Thanks... -- The above message is encrypted with double rot13 encoding. Any unauthorized attempt to decrypt it will be prosecuted to the full extent of the law.