Rather than run the job every 2 minutes why not use SQL Server Agent to run the job when it detects a blocked session?
1) Set server "blocked process threshold (s)" to the number of seconds after which you want the alert fired
2) Create an alert in the agent
- type="SQL Server performance condition alert",
- counter = "Processed blocked",
- alert if counter ="rises above" ,
- value = "0".
3) On the "response" tab, execute your job.(or any job that queries who's blocking who) and email it to yourself.