c# and Exchange 2003 Logs

Question

Okay, I've been tasked with trying to find out how many emails were unsuccessful once I broadcast an email to many subscribers. I've been looking at Log parser 2.2 and it seems to allow me to parse it into a csv file in which I can process using asp. I kind of want to create a program in C# that every five minutes parses the exchange log. Since the exchange log only logs the successful one, subtract successful attempts from total attempts and that's my missing amount. I guess my question is, should I schedule a program to run every five minutes or listen for the file to change? If listen for the file to change how exactly would I do that? Or if there is already a wheel invented for this type of subject what's the resource? Wouldn't want to reinvent the wheel. Thanks, Josh