Checking runtime within script

[sshafe]

I've been researching without any success, and I don't know if this can even be done, but here it goes:

I am trying to write a script that will kick off defrags against multiple SQL server drives. My issue, is that I need to check the status of the different defrags that are running and to make sure they do not run too long.

Is there a way to check within a script, say every 30 minutes, the elasped runtime of the script?

Thanks in advance