Hello,
The triggering technique you are looking for is pause triggering. I have attached a VI that acquires data when the trigger level is above 5V, and pauses the acquisition when the trigger level is below 5V. As for finding the peak values, you will need to do some post-acquisition processing. You might want to take a look at the Array Max & Min VI on the Array sub-pallette. Hope this helps.
-Alan A.