stopping a test dynamically

[bgordon]

I'd like to run an unattended test that stresses a system until it "breaks". 
I'd like to define "break" dynamically, say for example when a certain type of 
transaction has its avg response time for the last 2 minutes > some threshold. 
When this condition occurs I'd like to stop the test. Can this be done and if 
so what technique would you suggest. Thanks, -Bruce