Alerts For Changes To Fields In SQL

I'm creating a Process Control application that will save various data fields to SQL Server 2005. Part of the data will be input via a VB hand-held application which was created on the CE 5.0 - we are running VB.NET 2.0 on Visual Studio 2005. The rest of the data will be collected via plant equipment which will interface will PLCs on the production floor. There are approximately 25 different attributes which will be stored in a SQL server table.

The user wants me to create 3 alert levels that will involve:
1) Checking to see IF a reading was manually input.
2) Checking to see if the value passed or failed.

The FIRST alert involves notifying the operator via the hand-held or some other technique. The SECOND alert involves checking back after a set time interval (15 minutes, 30 minutes, etc.) to see if the attribute passed or failed and then taking a higher action - such as an email, text message or phone call to a higher level manager. If the second check fails, the same escalation process continues with the THIRD alert level - and another action takes place such as a message being sent to yet a higher level manager.

Presumably, once the status check passes, the alert level is re-set back to 0. But I'm thinking that the process that checks for the failed attributes will need to continue to run in the background - probably at set intervals. I'm not sure if the functionality for this is something that would be best handled by VB.NET or SQL Server...